Active Record objects don‘t specify their attributes directly, but rather infer them from the table definition with which they‘re linked. Adding, removing, and changing attributes and their type is done directly in the database. Any change is instantly reflected in the Active Record objects. The mapping that binds a given Active Record class to a certain database table will happen automatically in most common cases, but can be overwritten for the uncommon ones.

See the mapping rules in table_name and the full example in files/README.html for more insight.


Active Records accept constructor parameters either in a hash or as a block. The hash method is especially useful when you‘re receiving the data from somewhere else, like an HTTP request. It works like this:

  user = => "David", :occupation => "Code Artist") # => "David"

You can also use block initialization:

  user = do |u| = "David"
    u.occupation = "Code Artist"

And of course you can just create a bare object and specify the attributes after the fact:

  user = = "David"
  user.occupation = "Code Artist"


Conditions can either be specified as a string, array, or hash representing the WHERE-part of an SQL statement. The array form is to be used when the condition input is tainted and requires sanitization. The string form can be used for statements that don‘t involve tainted data. The hash form works much like the array form, except only equality and range is possible. Examples:

  class User < ActiveRecord::Base
    def self.authenticate_unsafely(user_name, password)
      find(:first, :conditions => "user_name = '#{user_name}' AND password = '#{password}'")

    def self.authenticate_safely(user_name, password)
      find(:first, :conditions => [ "user_name = ? AND password = ?", user_name, password ])

    def self.authenticate_safely_simply(user_name, password)
      find(:first, :conditions => { :user_name => user_name, :password => password })

The authenticate_unsafely method inserts the parameters directly into the query and is thus susceptible to SQL-injection attacks if the user_name and password parameters come directly from an HTTP request. The authenticate_safely and authenticate_safely_simply both will sanitize the user_name and password before inserting them in the query, which will ensure that an attacker can‘t escape the query and fake the login (or worse).

When using multiple parameters in the conditions, it can easily become hard to read exactly what the fourth or fifth question mark is supposed to represent. In those cases, you can resort to named bind variables instead. That‘s done by replacing the question marks with symbols and supplying a hash with values for the matching symbol keys:

  Company.find(:first, :conditions => [
    "id = :id AND name = :name AND division = :division AND created_at > :accounting_date",
    { :id => 3, :name => "37signals", :division => "First", :accounting_date => '2005-01-01' }

Similarly, a simple hash without a statement will generate conditions based on equality with the SQL AND operator. For instance:

  Student.find(:all, :conditions => { :first_name => "Harvey", :status => 1 })
  Student.find(:all, :conditions => params[:student])

A range may be used in the hash to use the SQL BETWEEN operator:

  Student.find(:all, :conditions => { :grade => 9..12 })

An array may be used in the hash to use the SQL IN operator:

  Student.find(:all, :conditions => { :grade => [9,11,12] })

Overwriting default accessors

All column values are automatically available through basic accessors on the Active Record object, but sometimes you want to specialize this behavior. This can be done by overwriting the default accessors (using the same name as the attribute) and calling read_attribute(attr_name) and write_attribute(attr_name, value) to actually change things. Example:

  class Song < ActiveRecord::Base
    # Uses an integer of seconds to hold the length of the song

    def length=(minutes)
      write_attribute(:length, minutes.to_i * 60)

    def length
      read_attribute(:length) / 60

You can alternatively use self[:attribute]=(value) and self[:attribute] instead of write_attribute(:attribute, value) and read_attribute(:attribute) as a shorter form.

Attribute query methods

In addition to the basic accessors, query methods are also automatically available on the Active Record object. Query methods allow you to test whether an attribute value is present.

For example, an Active Record User with the name attribute has a name? method that you can call to determine whether the user has a name:

  user = => "David") # => true

  anonymous = => "") # => false

Accessing attributes before they have been typecasted

Sometimes you want to be able to read the raw attribute data without having the column-determined typecast run its course first. That can be done by using the <attribute>_before_type_cast accessors that all attributes have. For example, if your Account model has a balance attribute, you can call account.balance_before_type_cast or account.id_before_type_cast.

This is especially useful in validation situations where the user might supply a string for an integer field and you want to display the original string back in an error message. Accessing the attribute normally would typecast the string to 0, which isn‘t what you want.

Dynamic attribute-based finders

Dynamic attribute-based finders are a cleaner way of getting (and/or creating) objects by simple queries without turning to SQL. They work by appending the name of an attribute to find_by_, find_last_by_, or find_all_by_, so you get finders like Person.find_by_user_name, Person.find_all_by_last_name, and Payment.find_by_transaction_id. So instead of writing Person.find(:first, :conditions => ["user_name = ?", user_name]), you just do Person.find_by_user_name(user_name). And instead of writing Person.find(:all, :conditions => ["last_name = ?", last_name]), you just do Person.find_all_by_last_name(last_name).

It‘s also possible to use multiple attributes in the same find by separating them with "and", so you get finders like Person.find_by_user_name_and_password or even Payment.find_by_purchaser_and_state_and_country. So instead of writing Person.find(:first, :conditions => ["user_name = ? AND password = ?", user_name, password]), you just do Person.find_by_user_name_and_password(user_name, password).

It‘s even possible to use all the additional parameters to find. For example, the full interface for Payment.find_all_by_amount is actually Payment.find_all_by_amount(amount, options). And the full interface to Person.find_by_user_name is actually Person.find_by_user_name(user_name, options). So you could call Payment.find_all_by_amount(50, :order => "created_on"). Also you may call Payment.find_last_by_amount(amount, options) returning the last record matching that amount and options.

The same dynamic finder style can be used to create the object if it doesn‘t already exist. This dynamic finder is called with find_or_create_by_ and will return the object if it already exists and otherwise creates it, then returns it. Protected attributes won‘t be set unless they are given in a block. For example:

  # No 'Summer' tag exists
  Tag.find_or_create_by_name("Summer") # equal to Tag.create(:name => "Summer")

  # Now the 'Summer' tag does exist
  Tag.find_or_create_by_name("Summer") # equal to Tag.find_by_name("Summer")

  # Now 'Bob' exist and is an 'admin'
  User.find_or_create_by_name('Bob', :age => 40) { |u| u.admin = true }

Use the find_or_initialize_by_ finder if you want to return a new record without saving it first. Protected attributes won‘t be set unless they are given in a block. For example:

  # No 'Winter' tag exists
  winter = Tag.find_or_initialize_by_name("Winter")
  winter.new_record? # true

To find by a subset of the attributes to be used for instantiating a new object, pass a hash instead of a list of parameters. For example:

  Tag.find_or_create_by_name(:name => "rails", :creator => current_user)

That will either find an existing tag named "rails", or create a new one while setting the user that created it.

Saving arrays, hashes, and other non-mappable objects in text columns

Active Record can serialize any object in text columns using YAML. To do so, you must specify this with a call to the class method serialize. This makes it possible to store arrays, hashes, and other non-mappable objects without doing any additional work. Example:

  class User < ActiveRecord::Base
    serialize :preferences

  user = User.create(:preferences => { "background" => "black", "display" => large })
  User.find( # => { "background" => "black", "display" => large }

You can also specify a class option as the second parameter that‘ll raise an exception if a serialized object is retrieved as a descendant of a class not in the hierarchy. Example:

  class User < ActiveRecord::Base
    serialize :preferences, Hash

  user = User.create(:preferences => %w( one two three ))
  User.find(    # raises SerializationTypeMismatch

Single table inheritance

Active Record allows inheritance by storing the name of the class in a column that by default is named "type" (can be changed by overwriting Base.inheritance_column). This means that an inheritance looking like this:

  class Company < ActiveRecord::Base; end
  class Firm < Company; end
  class Client < Company; end
  class PriorityClient < Client; end

When you do Firm.create(:name => "37signals"), this record will be saved in the companies table with type = "Firm". You can then fetch this row again using Company.find(:first, "name = ‘37signals’") and it will return a Firm object.

If you don‘t have a type column defined in your table, single-table inheritance won‘t be triggered. In that case, it‘ll work just like normal subclasses with no special magic for differentiating between them or reloading the right type with find.

Note, all the attributes for all the cases are kept in the same table. Read more:

Connection to multiple databases in different models

Connections are usually created through ActiveRecord::Base.establish_connection and retrieved by ActiveRecord::Base.connection. All classes inheriting from ActiveRecord::Base will use this connection. But you can also set a class-specific connection. For example, if Course is an ActiveRecord::Base, but resides in a different database, you can just say Course.establish_connection and Course and all of its subclasses will use this connection instead.

This feature is implemented by keeping a connection pool in ActiveRecord::Base that is a Hash indexed by the class. If a connection is requested, the retrieve_connection method will go up the class-hierarchy until a connection is found in the connection pool.


Note: The attributes listed are class-level attributes (accessible from both the class and instance level). So it‘s possible to assign a logger to the class through Base.logger= which will then be used by all instances in the current object space.

VALID_FIND_OPTIONS = [ :conditions, :include, :joins, :limit, :offset, :order, :select, :readonly, :group, :having, :from, :lock ]
[RW] abstract_class Set this to true if this is an abstract class (see abstract_class?).
Public Class methods

Overwrite the default class equality method to provide support for association proxies.

      # File activerecord/lib/active_record/base.rb, line 1489
1489:       def ===(object)
1490:         object.is_a?(self)
1491:       end

Returns whether this class is a base AR class. If A is a base class and B descends from A, then B.base_class will return B.

      # File activerecord/lib/active_record/base.rb, line 1505
1505:       def abstract_class?
1506:         defined?(@abstract_class) && @abstract_class == true
1507:       end

This is an alias for find(:all). You can pass in all the same arguments to this method as you can to find(:all)

     # File activerecord/lib/active_record/base.rb, line 638
638:       def all(*args)
639:         find(:all, *args)
640:       end

Deprecated and no longer has any effect.

    # File activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 92
92:       def allow_concurrency
93:         ActiveSupport::Deprecation.warn("ActiveRecord::Base.allow_concurrency has been deprecated and no longer has any effect. Please remove all references to allow_concurrency.")
94:       end

Deprecated and no longer has any effect.

    # File activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 97
97:       def allow_concurrency=(flag)
98:         ActiveSupport::Deprecation.warn("ActiveRecord::Base.allow_concurrency= has been deprecated and no longer has any effect. Please remove all references to allow_concurrency=.")
99:       end

Specifies a white list of model attributes that can be set via mass-assignment, such as new(attributes), update_attributes(attributes), or attributes=(attributes)

This is the opposite of the attr_protected macro: Mass-assignment will only set attributes in this list, to assign to the rest of attributes you can use direct writer methods. This is meant to protect sensitive attributes from being overwritten by malicious users tampering with URLs or forms. If you‘d rather start from an all-open default and restrict attributes as needed, have a look at attr_protected.

  class Customer < ActiveRecord::Base
    attr_accessible :name, :nickname

  customer = => "David", :nickname => "Dave", :credit_rating => "Excellent")
  customer.credit_rating # => nil
  customer.attributes = { :name => "Jolly fellow", :credit_rating => "Superb" }
  customer.credit_rating # => nil

  customer.credit_rating = "Average"
  customer.credit_rating # => "Average"
      # File activerecord/lib/active_record/base.rb, line 1086
1086:       def attr_accessible(*attributes)
1087:         write_inheritable_attribute(:attr_accessible, + (accessible_attributes || []))
1088:       end

Attributes named in this macro are protected from mass-assignment, such as new(attributes), update_attributes(attributes), or attributes=(attributes).

Mass-assignment to these attributes will simply be ignored, to assign to them you can use direct writer methods. This is meant to protect sensitive attributes from being overwritten by malicious users tampering with URLs or forms.

  class Customer < ActiveRecord::Base
    attr_protected :credit_rating

  customer ="name" => David, "credit_rating" => "Excellent")
  customer.credit_rating # => nil
  customer.attributes = { "description" => "Jolly fellow", "credit_rating" => "Superb" }
  customer.credit_rating # => nil

  customer.credit_rating = "Average"
  customer.credit_rating # => "Average"

To start from an all-closed default and enable attributes as needed, have a look at attr_accessible.

      # File activerecord/lib/active_record/base.rb, line 1053
1053:       def attr_protected(*attributes)
1054:         write_inheritable_attribute(:attr_protected, + (protected_attributes || []))
1055:       end

Attributes listed as readonly can be set for a new record, but will be ignored in database updates afterwards.

      # File activerecord/lib/active_record/base.rb, line 1096
1096:        def attr_readonly(*attributes)
1097:          write_inheritable_attribute(:attr_readonly, + (readonly_attributes || []))
1098:        end

Returns the base AR subclass that this class descends from. If A extends AR::Base, A.base_class will return A. If B descends from A through some arbitrarily deep hierarchy, B.base_class will return A.

      # File activerecord/lib/active_record/base.rb, line 1496
1496:       def base_class
1497:         class_of_active_record_descendant(self)
1498:       end
benchmark(title, log_level = Logger::DEBUG, use_silence = true) {|| ...}

Log and benchmark multiple statements in a single block. Example:

  Project.benchmark("Creating project") do
    project = Project.create("name" => "stuff")
    project.create_manager("name" => "David")
    project.milestones << Milestone.find(:all)

The benchmark is only recorded if the current level of the logger is less than or equal to the log_level, which makes it easy to include benchmarking statements in production software that will remain inexpensive because the benchmark will only be conducted if the log level is low enough.

The logging of the multiple statements is turned off unless use_silence is set to false.

      # File activerecord/lib/active_record/base.rb, line 1469
1469:       def benchmark(title, log_level = Logger::DEBUG, use_silence = true)
1470:         if logger && logger.level <= log_level
1471:           result = nil
1472:           ms = { result = use_silence ? silence { yield } : yield }
1473:           logger.add(log_level, '%s (%.1fms)' % [title, ms])
1474:           result
1475:         else
1476:           yield
1477:         end
1478:       end

Returns an array of column names as strings.

      # File activerecord/lib/active_record/base.rb, line 1318
1318:       def column_names
1319:         @column_names ||= { |column| }
1320:       end

Returns an array of column objects for the table associated with this class.

      # File activerecord/lib/active_record/base.rb, line 1304
1304:       def columns
1305:         unless defined?(@columns) && @columns
1306:           @columns = connection.columns(table_name, "#{name} Columns")
1307:           @columns.each { |column| column.primary = == primary_key }
1308:         end
1309:         @columns
1310:       end

Returns a hash of column objects for the table associated with this class.

      # File activerecord/lib/active_record/base.rb, line 1313
1313:       def columns_hash
1314:         @columns_hash ||= columns.inject({}) { |hash, column| hash[] = column; hash }
1315:       end

Returns true if ActiveRecord is connected.

     # File activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 127
127:       def connected?
128:         connection_handler.connected?(self)
129:       end

Returns the connection currently associated with the class. This can also be used to "borrow" the connection to do database work unrelated to any of the specific Active Records.

     # File activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 114
114:       def connection
115:         retrieve_connection
116:       end
     # File activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 118
118:       def connection_pool
119:         connection_handler.retrieve_connection_pool(self)
120:       end

Returns an array of column objects where the primary id, all columns ending in "_id" or "_count", and columns used for single table inheritance have been removed.

      # File activerecord/lib/active_record/base.rb, line 1324
1324:       def content_columns
1325:         @content_columns ||= columns.reject { |c| c.primary || =~ /(_id|_count)$/ || == inheritance_column }
1326:       end

Returns the result of an SQL statement that should only include a COUNT(*) in the SELECT part. The use of this method should be restricted to complicated SQL queries that can‘t be executed using the ActiveRecord::Calculations class methods. Look into those before using this.


  • sql - An SQL statement which should return a count query from the database, see the example below.


  Product.count_by_sql "SELECT COUNT(*) FROM sales s, customers c WHERE s.customer_id ="
     # File activerecord/lib/active_record/base.rb, line 918
918:       def count_by_sql(sql)
919:         sql = sanitize_conditions(sql)
920:         connection.select_value(sql, "#{name} Count").to_i
921:       end
create(attributes = nil) {|object| ...}

Creates an object (or multiple objects) and saves it to the database, if validations pass. The resulting object is returned whether the object was saved successfully to the database or not.

The attributes parameter can be either be a Hash or an Array of Hashes. These Hashes describe the attributes on the objects that are to be created.


  # Create a single new object
  User.create(:first_name => 'Jamie')

  # Create an Array of new objects
  User.create([{ :first_name => 'Jamie' }, { :first_name => 'Jeremy' }])

  # Create a single object and pass it into a block to set other attributes.
  User.create(:first_name => 'Jamie') do |u|
    u.is_admin = false

  # Creating an Array of new objects using a block, where the block is executed for each object:
  User.create([{ :first_name => 'Jamie' }, { :first_name => 'Jeremy' }]) do |u|
    u.is_admin = false
     # File activerecord/lib/active_record/base.rb, line 721
721:       def create(attributes = nil, &block)
722:         if attributes.is_a?(Array)
723:           attributes.collect { |attr| create(attr, &block) }
724:         else
725:           object = new(attributes)
726:           yield(object) if block_given?
728:           object
729:         end
730:       end
decrement_counter(counter_name, id)

Decrement a number field by one, usually representing a count.

This works the same as increment_counter but reduces the column value by 1 instead of increasing it.


  • counter_name - The name of the field that should be decremented.
  • id - The id of the object that should be decremented.


  # Decrement the post_count column for the record with an id of 5
  DiscussionBoard.decrement_counter(:post_count, 5)
      # File activerecord/lib/active_record/base.rb, line 1025
1025:       def decrement_counter(counter_name, id)
1026:         update_counters(id, counter_name => -1)
1027:       end

Deletes the row with a primary key matching the id argument, using a SQL DELETE statement, and returns the number of rows deleted. Active Record objects are not instantiated, so the object‘s callbacks are not executed, including any :dependent association options or Observer methods.

You can delete multiple rows at once by passing an Array of ids.

Note: Although it is often much faster than the alternative, destroy, skipping callbacks might bypass business logic in your application that ensures referential integrity or performs other essential jobs.


  # Delete a single row

  # Delete multiple rows
     # File activerecord/lib/active_record/base.rb, line 779
779:       def delete(id)
780:         delete_all([ "#{connection.quote_column_name(primary_key)} IN (?)", id ])
781:       end
delete_all(conditions = nil)

Deletes the records matching conditions without instantiating the records first, and hence not calling the destroy method nor invoking callbacks. This is a single SQL DELETE statement that goes straight to the database, much more efficient than destroy_all. Be careful with relations though, in particular :dependent rules defined on associations are not honored. Returns the number of rows affected.


  • conditions - Conditions are specified the same way as with find method.


  Post.delete_all("person_id = 5 AND (category = 'Something' OR category = 'Else')")
  Post.delete_all(["person_id = ? AND (category = ? OR category = ?)", 5, 'Something', 'Else'])

Both calls delete the affected posts all at once with a single DELETE statement. If you need to destroy dependent associations or call your before_* or after_destroy callbacks, use the destroy_all method instead.

     # File activerecord/lib/active_record/base.rb, line 901
901:       def delete_all(conditions = nil)
902:         sql = "DELETE FROM #{quoted_table_name} "
903:         add_conditions!(sql, conditions, scope(:find))
904:         connection.delete(sql, "#{name} Delete all")
905:       end

True if this isn‘t a concrete subclass needing a STI type condition.

      # File activerecord/lib/active_record/base.rb, line 1420
1420:       def descends_from_active_record?
1421:         if superclass.abstract_class?
1422:           superclass.descends_from_active_record?
1423:         else
1424:           superclass == Base || !columns_hash.include?(inheritance_column)
1425:         end
1426:       end

Destroy an object (or multiple objects) that has the given id, the object is instantiated first, therefore all callbacks and filters are fired off before the object is deleted. This method is less efficient than ActiveRecord#delete but allows cleanup methods and other actions to be run.

This essentially finds the object (or multiple objects) with the given id, creates a new object from the attributes, and then calls destroy on it.


  • id - Can be either an Integer or an Array of Integers.


  # Destroy a single object

  # Destroy multiple objects
  todos = [1,2,3]
     # File activerecord/lib/active_record/base.rb, line 802
802:       def destroy(id)
803:         if id.is_a?(Array)
804:  { |one_id| destroy(one_id) }
805:         else
806:           find(id).destroy
807:         end
808:       end
destroy_all(conditions = nil)

Destroys the records matching conditions by instantiating each record and calling its destroy method. Each object‘s callbacks are executed (including :dependent association options and before_destroy/after_destroy Observer methods). Returns the collection of objects that were destroyed; each will be frozen, to reflect that no changes should be made (since they can‘t be persisted).

Note: Instantiation, callback execution, and deletion of each record can be time consuming when you‘re removing many records at once. It generates at least one SQL DELETE query per record (or possibly more, to enforce your callbacks). If you want to delete many rows quickly, without concern for their associations or callbacks, use delete_all instead.


  • conditions - A string, array, or hash that specifies which records to destroy. If omitted, all records are destroyed. See the Conditions section in the introduction to ActiveRecord::Base for more information.


  Person.destroy_all("last_login < '2004-04-04'")
  Person.destroy_all(:status => "inactive")
     # File activerecord/lib/active_record/base.rb, line 880
880:       def destroy_all(conditions = nil)
881:         find(:all, :conditions => conditions).each { |object| object.destroy }
882:       end
establish_connection(spec = nil)

Establishes the connection to the database. Accepts a hash as input where the :adapter key must be specified with the name of a database adapter (in lower-case) example for regular databases (MySQL, Postgresql, etc):

    :adapter  => "mysql",
    :host     => "localhost",
    :username => "myuser",
    :password => "mypass",
    :database => "somedatabase"

Example for SQLite database:

    :adapter => "sqlite",
    :database  => "path/to/dbfile"

Also accepts keys as strings (for parsing from YAML for example):

    "adapter" => "sqlite",
    "database"  => "path/to/dbfile"

The exceptions AdapterNotSpecified, AdapterNotFound and ArgumentError may be returned on an error.

    # File activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 51
51:     def self.establish_connection(spec = nil)
52:       case spec
53:         when nil
54:           raise AdapterNotSpecified unless defined? RAILS_ENV
55:           establish_connection(RAILS_ENV)
56:         when ConnectionSpecification
57:           self.connection_handler.establish_connection(name, spec)
58:         when Symbol, String
59:           if configuration = configurations[spec.to_s]
60:             establish_connection(configuration)
61:           else
62:             raise AdapterNotSpecified, "#{spec} database is not configured"
63:           end
64:         else
65:           spec = spec.symbolize_keys
66:           unless spec.key?(:adapter) then raise AdapterNotSpecified, "database configuration does not specify adapter" end
68:           begin
69:             require 'rubygems'
70:             gem "activerecord-#{spec[:adapter]}-adapter"
71:             require "active_record/connection_adapters/#{spec[:adapter]}_adapter"
72:           rescue LoadError
73:             begin
74:               require "active_record/connection_adapters/#{spec[:adapter]}_adapter"
75:             rescue LoadError
76:               raise "Please install the #{spec[:adapter]} adapter: `gem install activerecord-#{spec[:adapter]}-adapter` (#{$!})"
77:             end
78:           end
80:           adapter_method = "#{spec[:adapter]}_connection"
81:           if !respond_to?(adapter_method)
82:             raise AdapterNotFound, "database configuration specifies nonexistent #{spec[:adapter]} adapter"
83:           end
85:           remove_connection
86:           establish_connection(, adapter_method))
87:       end
88:     end
exists?(id_or_conditions = {})

Returns true if a record exists in the table that matches the id or conditions given, or false otherwise. The argument can take five forms:

  • Integer - Finds the record with this primary key.
  • String - Finds the record with a primary key corresponding to this string (such as ‘5‘).
  • Array - Finds the record that matches these find-style conditions (such as [‘color = ?’, ‘red’]).
  • Hash - Finds the record that matches these find-style conditions (such as {:color => ‘red’}).
  • No args - Returns false if the table is empty, true otherwise.

For more information about specifying conditions as a Hash or Array, see the Conditions section in the introduction to ActiveRecord::Base.

Note: You can‘t pass in a condition as a string (like name = ‘Jamie‘), since it would be sanitized and then queried against the primary key column, like id = ‘name = \’Jamie\’‘.


  Person.exists?(:name => "David")
  Person.exists?(['name LIKE ?', "%#{query}%"])
     # File activerecord/lib/active_record/base.rb, line 693
693:       def exists?(id_or_conditions = {})
694:         find_initial(
695:           :select => "#{quoted_table_name}.#{primary_key}",
696:           :conditions => expand_id_conditions(id_or_conditions)) ? true : false
697:       end

Find operates with four different retrieval approaches:

  • Find by id - This can either be a specific id (1), a list of ids (1, 5, 6), or an array of ids ([5, 6, 10]). If no record can be found for all of the listed ids, then RecordNotFound will be raised.
  • Find first - This will return the first record matched by the options used. These options can either be specific conditions or merely an order. If no record can be matched, nil is returned. Use Model.find(:first, *args) or its shortcut Model.first(*args).
  • Find last - This will return the last record matched by the options used. These options can either be specific conditions or merely an order. If no record can be matched, nil is returned. Use Model.find(:last, *args) or its shortcut Model.last(*args).
  • Find all - This will return all the records matched by the options used. If no records are found, an empty array is returned. Use Model.find(:all, *args) or its shortcut Model.all(*args).

All approaches accept an options hash as their last parameter.


  • :conditions - An SQL fragment like "administrator = 1", [ "user_name = ?", username ], or ["user_name = :user_name", { :user_name => user_name }]. See conditions in the intro.
  • :order - An SQL fragment like "created_at DESC, name".
  • :group - An attribute name by which the result should be grouped. Uses the GROUP BY SQL-clause.
  • :having - Combined with +:group+ this can be used to filter the records that a GROUP BY returns. Uses the HAVING SQL-clause.
  • :limit - An integer determining the limit on the number of rows that should be returned.
  • :offset - An integer determining the offset from where the rows should be fetched. So at 5, it would skip rows 0 through 4.
  • :joins - Either an SQL fragment for additional joins like "LEFT JOIN comments ON comments.post_id = id" (rarely needed), named associations in the same form used for the :include option, which will perform an INNER JOIN on the associated table(s), or an array containing a mixture of both strings and named associations. If the value is a string, then the records will be returned read-only since they will have attributes that do not correspond to the table‘s columns. Pass :readonly => false to override.
  • :include - Names associations that should be loaded alongside. The symbols named refer to already defined associations. See eager loading under Associations.
  • :select - By default, this is "*" as in "SELECT * FROM", but can be changed if you, for example, want to do a join but not include the joined columns. Takes a string with the SELECT SQL fragment (e.g. "id, name").
  • :from - By default, this is the table name of the class, but can be changed to an alternate table name (or even the name of a database view).
  • :readonly - Mark the returned records read-only so they cannot be saved or updated.
  • :lock - An SQL fragment like "FOR UPDATE" or "LOCK IN SHARE MODE". :lock => true gives connection‘s default exclusive lock, usually "FOR UPDATE".


  # find by id
  Person.find(1)       # returns the object for ID = 1
  Person.find(1, 2, 6) # returns an array for objects with IDs in (1, 2, 6)
  Person.find([7, 17]) # returns an array for objects with IDs in (7, 17)
  Person.find([1])     # returns an array for the object with ID = 1
  Person.find(1, :conditions => "administrator = 1", :order => "created_on DESC")

Note that returned records may not be in the same order as the ids you provide since database rows are unordered. Give an explicit :order to ensure the results are sorted.


  # find first
  Person.find(:first) # returns the first object fetched by SELECT * FROM people
  Person.find(:first, :conditions => [ "user_name = ?", user_name])
  Person.find(:first, :conditions => [ "user_name = :u", { :u => user_name }])
  Person.find(:first, :order => "created_on DESC", :offset => 5)

  # find last
  Person.find(:last) # returns the last object fetched by SELECT * FROM people
  Person.find(:last, :conditions => [ "user_name = ?", user_name])
  Person.find(:last, :order => "created_on DESC", :offset => 5)

  # find all
  Person.find(:all) # returns an array of objects for all the rows fetched by SELECT * FROM people
  Person.find(:all, :conditions => [ "category IN (?)", categories], :limit => 50)
  Person.find(:all, :conditions => { :friends => ["Bob", "Steve", "Fred"] }
  Person.find(:all, :offset => 10, :limit => 10)
  Person.find(:all, :include => [ :account, :friends ])
  Person.find(:all, :group => "category")

Example for find with a lock: Imagine two concurrent transactions: each will read person.visits == 2, add 1 to it, and save, resulting in two saves of person.visits = 3. By locking the row, the second transaction has to wait until the first is finished; we get the expected person.visits == 4.

  Person.transaction do
    person = Person.find(1, :lock => true)
    person.visits += 1!
     # File activerecord/lib/active_record/base.rb, line 611
611:       def find(*args)
612:         options = args.extract_options!
613:         validate_find_options(options)
614:         set_readonly_option!(options)
616:         case args.first
617:           when :first then find_initial(options)
618:           when :last  then find_last(options)
619:           when :all   then find_every(options)
620:           else             find_from_ids(args, options)
621:         end
622:       end

Executes a custom SQL query against your database and returns all the results. The results will be returned as an array with columns requested encapsulated as attributes of the model you call this method from. If you call Product.find_by_sql then the results will be returned in a Product object with the attributes you specified in the SQL query.

If you call a complicated SQL query which spans multiple tables the columns specified by the SELECT will be attributes of the model, whether or not they are columns of the corresponding table.

The sql parameter is a full SQL query as a string. It will be called as is, there will be no database agnostic conversions performed. This should be a last resort because using, for example, MySQL specific terms will lock you to using that particular database engine or require you to change your call if you switch engines.


  # A simple SQL query spanning multiple tables
  Post.find_by_sql "SELECT p.title, FROM posts p, comments c WHERE = c.post_id"
  > [#<Post:0x36bff9c @attributes={"title"=>"Ruby Meetup", "first_name"=>"Quentin"}>, ...]

  # You can use the same string replacement techniques as you can with ActiveRecord#find
  Post.find_by_sql ["SELECT title FROM posts WHERE author = ? AND created > ?", author_id, start_date]
  > [#<Post:0x36bff9c @attributes={"first_name"=>"The Cheap Man Buys Twice"}>, ...]
     # File activerecord/lib/active_record/base.rb, line 664
664:       def find_by_sql(sql)
665:         connection.select_all(sanitize_sql(sql), "#{name} Load").collect! { |record| instantiate(record) }
666:       end

A convenience wrapper for find(:first, *args). You can pass in all the same arguments to this method as you can to find(:first).

     # File activerecord/lib/active_record/base.rb, line 626
626:       def first(*args)
627:         find(:first, *args)
628:       end
human_attribute_name(attribute_key_name, options = {})

Transforms attribute key names into a more humane format, such as "First name" instead of "first_name". Example:

  Person.human_attribute_name("first_name") # => "First name"

This used to be depricated in favor of humanize, but is now preferred, because it automatically uses the I18n module now. Specify options with additional translating options.

      # File activerecord/lib/active_record/base.rb, line 1396
1396:       def human_attribute_name(attribute_key_name, options = {})
1397:         defaults = do |klass|
1398:           "#{}.#{attribute_key_name}""#{}.#{attribute_key_name}"
1399:         end
1400:         defaults << options[:default] if options[:default]
1401:         defaults.flatten!
1402:         defaults << attribute_key_name.to_s.humanize
1403:         options[:count] ||= 1
1404:         I18n.translate(defaults.shift, options.merge(:default => defaults, :scope => [:activerecord, :attributes]))
1405:       end
human_name(options = {})

Transform the modelname into a more humane format, using I18n. Defaults to the basic humanize method. Default scope of the translation is activerecord.models Specify options with additional translating options.

      # File activerecord/lib/active_record/base.rb, line 1411
1411:       def human_name(options = {})
1412:         defaults = do |klass|
1413:           "#{}""#{}"
1414:         end 
1415:         defaults <<
1416:         I18n.translate(defaults.shift, {:scope => [:activerecord, :models], :count => 1, :default => defaults}.merge(options))
1417:       end
increment_counter(counter_name, id)

Increment a number field by one, usually representing a count.

This is used for caching aggregate values, so that they don‘t need to be computed every time. For example, a DiscussionBoard may cache post_count and comment_count otherwise every time the board is shown it would have to run an SQL query to find how many posts and comments there are.


  • counter_name - The name of the field that should be incremented.
  • id - The id of the object that should be incremented.


  # Increment the post_count column for the record with an id of 5
  DiscussionBoard.increment_counter(:post_count, 5)
      # File activerecord/lib/active_record/base.rb, line 1008
1008:       def increment_counter(counter_name, id)
1009:         update_counters(id, counter_name => 1)
1010:       end

Defines the column name for use with single table inheritance — can be set in subclasses like so: self.inheritance_column = "type_id"

      # File activerecord/lib/active_record/base.rb, line 1216
1216:       def inheritance_column
1217:         @inheritance_column ||= "type".freeze
1218:       end

Returns a string like ‘Post id:integer, title:string, body:text‘

      # File activerecord/lib/active_record/base.rb, line 1434
1434:       def inspect
1435:         if self == Base
1436:           super
1437:         elsif abstract_class?
1438:           "#{super}(abstract)"
1439:         elsif table_exists?
1440:           attr_list = { |c| "#{}: #{c.type}" } * ', '
1441:           "#{super}(#{attr_list})"
1442:         else
1443:           "#{super}(Table doesn't exist)"
1444:         end
1445:       end

A convenience wrapper for find(:last, *args). You can pass in all the same arguments to this method as you can to find(:last).

     # File activerecord/lib/active_record/base.rb, line 632
632:       def last(*args)
633:         find(:last, *args)
634:       end

Merges conditions so that the result is a valid condition

      # File activerecord/lib/active_record/base.rb, line 1524
1524:       def merge_conditions(*conditions)
1525:         segments = []
1527:         conditions.each do |condition|
1528:           unless condition.blank?
1529:             sql = sanitize_sql(condition)
1530:             segments << sql unless sql.blank?
1531:           end
1532:         end
1534:         "(#{segments.join(') AND (')})" unless segments.empty?
1535:       end
new(attributes = nil) {|self if block_given?| ...}

New objects can be instantiated as either empty (pass no construction parameter) or pre-set with attributes but not yet saved (pass a hash with key names matching the associated table column names). In both instances, valid attribute keys are determined by the column names of the associated table — hence you can‘t have attributes that aren‘t part of the table columns.

      # File activerecord/lib/active_record/base.rb, line 2476
2476:       def initialize(attributes = nil)
2477:         @attributes = attributes_from_column_definition
2478:         @attributes_cache = {}
2479:         @new_record = true
2480:         ensure_proper_type
2481:         self.attributes = attributes unless attributes.nil?
2482:         assign_attributes(self.class.send(:scope, :create)) if self.class.send(:scoped?, :create)
2483:         result = yield self if block_given?
2484:         callback(:after_initialize) if respond_to_without_attributes?(:after_initialize)
2485:         result
2486:       end

Defines the primary key field — can be overridden in subclasses. Overwriting will negate any effect of the primary_key_prefix_type setting, though.

      # File activerecord/lib/active_record/base.rb, line 1189
1189:       def primary_key
1190:         reset_primary_key
1191:       end

Returns an array of all the attributes that have been specified as readonly.

      # File activerecord/lib/active_record/base.rb, line 1101
1101:        def readonly_attributes
1102:          read_inheritable_attribute(:attr_readonly)
1103:        end
remove_connection(klass = self)
     # File activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 131
131:       def remove_connection(klass = self)
132:         connection_handler.remove_connection(klass)
133:       end

Resets all the cached information about columns, which will cause them to be reloaded on the next request.

The most common usage pattern for this method is probably in a migration, when just after creating a table you want to populate it with some default values, eg:

 class CreateJobLevels < ActiveRecord::Migration
   def self.up
     create_table :job_levels do |t|
       t.integer :id
       t.string :name


     %w{assistant executive manager director}.each do |type|
       JobLevel.create(:name => type)

   def self.down
     drop_table :job_levels
      # File activerecord/lib/active_record/base.rb, line 1368
1368:       def reset_column_information
1369:         generated_methods.each { |name| undef_method(name) }
1370:         @column_names = @columns = @columns_hash = @content_columns = @dynamic_methods_hash = @generated_methods = @inheritance_column = nil
1371:       end
reset_counters(id, *counters)

Resets one or more counter caches to their correct value using an SQL count query. This is useful when adding new counter caches, or if the counter has been corrupted or modified directly by SQL.


  • id - The id of the object you wish to reset a counter on.
  • counters - One or more counter names to reset


  # For Post with id #1 records reset the comments_count
  Post.reset_counters(1, :comments)
     # File activerecord/lib/active_record/base.rb, line 936
936:       def reset_counters(id, *counters)
937:         object = find(id)
938:         counters.each do |association|
939:           child_class = reflect_on_association(association.to_sym).klass
940:           belongs_name =
941:           counter_name = child_class.reflect_on_association(belongs_name).counter_cache_column
942:           value = object.send(association).count
944:           connection.update("UPDATE \#{quoted_table_name}\nSET \#{connection.quote_column_name(counter_name)} = \#{value}\nWHERE \#{connection.quote_column_name(primary_key)} = \#{quote_value(}\n", "#{name} UPDATE")
945:         end
946:         return true
947:       end
respond_to?(method_id, include_private = false)
      # File activerecord/lib/active_record/base.rb, line 1509
1509:       def respond_to?(method_id, include_private = false)
1510:         if match = DynamicFinderMatch.match(method_id)
1511:           return true if all_attributes_exists?(match.attribute_names)
1512:         elsif match = DynamicScopeMatch.match(method_id)
1513:           return true if all_attributes_exists?(match.attribute_names)
1514:         end
1516:         super
1517:       end
     # File activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 122
122:       def retrieve_connection
123:         connection_handler.retrieve_connection(self)
124:       end
serialize(attr_name, class_name = Object)

If you have an attribute that needs to be saved to the database as an object, and retrieved as the same object, then specify the name of that attribute using this method and it will be handled automatically. The serialization is done through YAML. If class_name is specified, the serialized object must be of that class on retrieval or SerializationTypeMismatch will be raised.


  • attr_name - The field name that should be serialized.
  • class_name - Optional, class name that the object type should be equal to.


  # Serialize a preferences attribute
  class User
    serialize :preferences
      # File activerecord/lib/active_record/base.rb, line 1120
1120:       def serialize(attr_name, class_name = Object)
1121:         serialized_attributes[attr_name.to_s] = class_name
1122:       end

Returns a hash of all the attributes that have been specified for serialization as keys and their class restriction as values.

      # File activerecord/lib/active_record/base.rb, line 1125
1125:       def serialized_attributes
1126:         read_inheritable_attribute(:attr_serialized) or write_inheritable_attribute(:attr_serialized, {})
1127:       end
set_inheritance_column(value = nil, &block)

Sets the name of the inheritance column to use to the given value, or (if the value # is nil or false) to the value returned by the given block.

  class Project < ActiveRecord::Base
    set_inheritance_column do
      original_inheritance_column + "_id"
      # File activerecord/lib/active_record/base.rb, line 1264
1264:       def set_inheritance_column(value = nil, &block)
1265:         define_attr_method :inheritance_column, value, &block
1266:       end
set_primary_key(value = nil, &block)

Sets the name of the primary key column to use to the given value, or (if the value is nil or false) to the value returned by the given block.

  class Project < ActiveRecord::Base
    set_primary_key "sysid"
      # File activerecord/lib/active_record/base.rb, line 1250
1250:       def set_primary_key(value = nil, &block)
1251:         define_attr_method :primary_key, value, &block
1252:       end
set_sequence_name(value = nil, &block)

Sets the name of the sequence to use when generating ids to the given value, or (if the value is nil or false) to the value returned by the given block. This is required for Oracle and is useful for any database which relies on sequences for primary key generation.

If a sequence name is not explicitly set when using Oracle or Firebird, it will default to the commonly used pattern of: #{table_name}_seq

If a sequence name is not explicitly set when using PostgreSQL, it will discover the sequence corresponding to your primary key for you.

  class Project < ActiveRecord::Base
    set_sequence_name "projectseq"   # default would have been "project_seq"
      # File activerecord/lib/active_record/base.rb, line 1283
1283:       def set_sequence_name(value = nil, &block)
1284:         define_attr_method :sequence_name, value, &block
1285:       end
set_table_name(value = nil, &block)

Sets the table name to use to the given value, or (if the value is nil or false) to the value returned by the given block.

  class Project < ActiveRecord::Base
    set_table_name "project"
      # File activerecord/lib/active_record/base.rb, line 1238
1238:       def set_table_name(value = nil, &block)
1239:         define_attr_method :table_name, value, &block
1240:       end
silence() {|| ...}

Silences the logger for the duration of the block.

      # File activerecord/lib/active_record/base.rb, line 1481
1481:       def silence
1482:         old_logger_level, logger.level = logger.level, Logger::ERROR if logger
1483:         yield
1484:       ensure
1485:         logger.level = old_logger_level if logger
1486:       end
      # File activerecord/lib/active_record/base.rb, line 1519
1519:       def sti_name
1520:         store_full_sti_class ? name : name.demodulize
1521:       end

Indicates whether the table associated with this class exists

      # File activerecord/lib/active_record/base.rb, line 1299
1299:       def table_exists?
1300:         connection.table_exists?(table_name)
1301:       end

Guesses the table name (in forced lower-case) based on the name of the class in the inheritance hierarchy descending directly from ActiveRecord::Base. So if the hierarchy looks like: Reply < Message < ActiveRecord::Base, then Message is used to guess the table name even when called on Reply. The rules used to do the guess are handled by the Inflector class in Active Support, which knows almost all common English inflections. You can add new inflections in config/initializers/inflections.rb.

Nested classes are given table names prefixed by the singular form of the parent‘s table name. Enclosing modules are not considered.


  class Invoice < ActiveRecord::Base; end;
  file                  class               table_name
  invoice.rb            Invoice             invoices

  class Invoice < ActiveRecord::Base; class Lineitem < ActiveRecord::Base; end; end;
  file                  class               table_name
  invoice.rb            Invoice::Lineitem   invoice_lineitems

  module Invoice; class Lineitem < ActiveRecord::Base; end; end;
  file                  class               table_name
  invoice/lineitem.rb   Invoice::Lineitem   lineitems

Additionally, the class-level table_name_prefix is prepended and the table_name_suffix is appended. So if you have "myapp_" as a prefix, the table name guess for an Invoice class becomes "myapp_invoices". Invoice::Lineitem becomes "myapp_invoice_lineitems".

You can also overwrite this class method to allow for unguessable links, such as a Mouse class with a link to a "mice" table. Example:

  class Mouse < ActiveRecord::Base
    set_table_name "mice"
      # File activerecord/lib/active_record/base.rb, line 1162
1162:       def table_name
1163:         reset_table_name
1164:       end
update(id, attributes)

Updates an object (or multiple objects) and saves it to the database, if validations pass. The resulting object is returned whether the object was saved successfully to the database or not.


  • id - This should be the id or an array of ids to be updated.
  • attributes - This should be a hash of attributes to be set on the object, or an array of hashes.


  # Updating one record:
  Person.update(15, :user_name => 'Samuel', :group => 'expert')

  # Updating multiple records:
  people = { 1 => { "first_name" => "David" }, 2 => { "first_name" => "Jeremy" } }
  Person.update(people.keys, people.values)
     # File activerecord/lib/active_record/base.rb, line 748
748:       def update(id, attributes)
749:         if id.is_a?(Array)
750:           idx = -1
751:           id.collect { |one_id| idx += 1; update(one_id, attributes[idx]) }
752:         else
753:           object = find(id)
754:           object.update_attributes(attributes)
755:           object
756:         end
757:       end
update_all(updates, conditions = nil, options = {})

Updates all records with details given if they match a set of conditions supplied, limits and order can also be supplied. This method constructs a single SQL UPDATE statement and sends it straight to the database. It does not instantiate the involved models and it does not trigger Active Record callbacks.


  • updates - A string of column and value pairs that will be set on any records that match conditions. This creates the SET clause of the generated SQL.
  • conditions - An SQL fragment like "administrator = 1" or [ "user_name = ?", username ]. See conditions in the intro for more info.
  • options - Additional options are :limit and :order, see the examples for usage.


  # Update all billing objects with the 3 different attributes given
  Billing.update_all( "category = 'authorized', approved = 1, author = 'David'" )

  # Update records that match our conditions
  Billing.update_all( "author = 'David'", "title LIKE '%Rails%'" )

  # Update records that match our conditions but limit it to 5 ordered by date
  Billing.update_all( "author = 'David'", "title LIKE '%Rails%'",
                        :order => 'created_at', :limit => 5 )
     # File activerecord/lib/active_record/base.rb, line 831
831:       def update_all(updates, conditions = nil, options = {})
832:         sql  = "UPDATE #{quoted_table_name} SET #{sanitize_sql_for_assignment(updates)} "
834:         scope = scope(:find)
836:         select_sql = ""
837:         add_conditions!(select_sql, conditions, scope)
839:         if options.has_key?(:limit) || (scope && scope[:limit])
840:           # Only take order from scope if limit is also provided by scope, this
841:           # is useful for updating a has_many association with a limit.
842:           add_order!(select_sql, options[:order], scope)
844:           add_limit!(select_sql, options, scope)
845:           sql.concat(connection.limited_update_conditions(select_sql, quoted_table_name, connection.quote_column_name(primary_key)))
846:         else
847:           add_order!(select_sql, options[:order], nil)
848:           sql.concat(select_sql)
849:         end
851:         connection.update(sql, "#{name} Update")
852:       end
update_counters(id, counters)

A generic "counter updater" implementation, intended primarily to be used by increment_counter and decrement_counter, but which may also be useful on its own. It simply does a direct SQL update for the record with the given ID, altering the given hash of counters by the amount given by the corresponding value:


  • id - The id of the object you wish to update a counter on or an Array of ids.
  • counters - An Array of Hashes containing the names of the fields to update as keys and the amount to update the field by as values.


  # For the Post with id of 5, decrement the comment_count by 1, and
  # increment the action_count by 1
  Post.update_counters 5, :comment_count => -1, :action_count => 1
  # Executes the following SQL:
  # UPDATE posts
  #    SET comment_count = comment_count - 1,
  #        action_count = action_count + 1
  #  WHERE id = 5

  # For the Posts with id of 10 and 15, increment the comment_count by 1
  Post.update_counters [10, 15], :comment_count => 1
  # Executes the following SQL:
  # UPDATE posts
  #    SET comment_count = comment_count + 1,
  #  WHERE id IN (10, 15)
     # File activerecord/lib/active_record/base.rb, line 983
983:       def update_counters(id, counters)
984:         updates = do |counter_name, value|
985:           operator = value < 0 ? '-' : '+'
986:           quoted_column = connection.quote_column_name(counter_name)
987:           "#{quoted_column} = COALESCE(#{quoted_column}, 0) #{operator} #{value.abs}"
988:         end
990:         update_all(updates.join(', '), primary_key => id )
991:       end

Deprecated and no longer has any effect.

     # File activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 102
102:       def verification_timeout
103:         ActiveSupport::Deprecation.warn("ActiveRecord::Base.verification_timeout has been deprecated and no longer has any effect. Please remove all references to verification_timeout.")
104:       end

Deprecated and no longer has any effect.

     # File activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 107
107:       def verification_timeout=(flag)
108:         ActiveSupport::Deprecation.warn("ActiveRecord::Base.verification_timeout= has been deprecated and no longer has any effect. Please remove all references to verification_timeout=.")
109:       end
Protected Class methods
      # File activerecord/lib/active_record/base.rb, line 2291
2291:         def aggregate_mapping(reflection)
2292:           mapping = reflection.options[:mapping] || [,]
2293:           mapping.first.is_a?(Array) ? mapping : [mapping]
2294:         end

Returns the class descending directly from ActiveRecord::Base or an abstract class, if any, in the inheritance hierarchy.

      # File activerecord/lib/active_record/base.rb, line 2249
2249:         def class_of_active_record_descendant(klass)
2250:           if klass.superclass == Base || klass.superclass.abstract_class?
2251:             klass
2252:           elsif klass.superclass.nil?
2253:             raise ActiveRecordError, "#{name} doesn't belong in a hierarchy descending from ActiveRecord"
2254:           else
2255:             class_of_active_record_descendant(klass.superclass)
2256:           end
2257:         end

Returns the class type of the record using the current module as a prefix. So descendants of MyApp::Business::Account would appear as MyApp::Business::AccountSubclass.

      # File activerecord/lib/active_record/base.rb, line 2236
2236:         def compute_type(type_name)
2237:           modularized_name = type_name_with_module(type_name)
2238:           silence_warnings do
2239:             begin
2240:               class_eval(modularized_name, __FILE__)
2241:             rescue NameError
2242:               class_eval(type_name, __FILE__)
2243:             end
2244:           end
2245:         end
default_scope(options = {})

Sets the default options for the model. The format of the options argument is the same as in find.

  class Person < ActiveRecord::Base
    default_scope :order => 'last_name, first_name'
      # File activerecord/lib/active_record/base.rb, line 2208
2208:         def default_scope(options = {})
2209:           self.default_scoping << { :find => options, :create => options[:conditions].is_a?(Hash) ? options[:conditions] : {} }
2210:         end

Accepts a hash of SQL conditions and replaces those attributes that correspond to a composed_of relationship with their expanded aggregate attribute values. Given:

    class Person < ActiveRecord::Base
      composed_of :address, :class_name => "Address",
        :mapping => [%w(address_street street), %w(address_city city)]


    { :address =>"813 abc st.", "chicago") }
      # => { :address_street => "813 abc st.", :address_city => "chicago" }
      # File activerecord/lib/active_record/base.rb, line 2307
2307:         def expand_hash_conditions_for_aggregates(attrs)
2308:           expanded_attrs = {}
2309:           attrs.each do |attr, value|
2310:             unless (aggregation = reflect_on_aggregation(attr.to_sym)).nil?
2311:               mapping = aggregate_mapping(aggregation)
2312:               mapping.each do |field_attr, aggregate_attr|
2313:                 if mapping.size == 1 && !value.respond_to?(aggregate_attr)
2314:                   expanded_attrs[field_attr] = value
2315:                 else
2316:                   expanded_attrs[field_attr] = value.send(aggregate_attr)
2317:                 end
2318:               end
2319:             else
2320:               expanded_attrs[attr] = value
2321:             end
2322:           end
2323:           expanded_attrs
2324:         end

Accepts an array of conditions. The array has each value sanitized and interpolated into the SQL statement.

  ["name='%s' and group_id='%s'", "foo'bar", 4]  returns  "name='foo''bar' and group_id='4'"
      # File activerecord/lib/active_record/base.rb, line 2379
2379:         def sanitize_sql_array(ary)
2380:           statement, *values = ary
2381:           if values.first.is_a?(Hash) and statement =~ /:\w+/
2382:             replace_named_bind_variables(statement, values.first)
2383:           elsif statement.include?('?')
2384:             replace_bind_variables(statement, values)
2385:           else
2386:             statement % values.collect { |value| connection.quote_string(value.to_s) }
2387:           end
2388:         end

Accepts an array, hash, or string of SQL conditions and sanitizes them into a valid SQL fragment for a SET clause.

  { :name => nil, :group_id => 4 }  returns "name = NULL , group_id='4'"
      # File activerecord/lib/active_record/base.rb, line 2283
2283:         def sanitize_sql_for_assignment(assignments)
2284:           case assignments
2285:             when Array; sanitize_sql_array(assignments)
2286:             when Hash;  sanitize_sql_hash_for_assignment(assignments)
2287:             else        assignments
2288:           end
2289:         end
sanitize_sql_for_conditions(condition, table_name = quoted_table_name)

Accepts an array, hash, or string of SQL conditions and sanitizes them into a valid SQL fragment for a WHERE clause.

  ["name='%s' and group_id='%s'", "foo'bar", 4]  returns  "name='foo''bar' and group_id='4'"
  { :name => "foo'bar", :group_id => 4 }  returns "name='foo''bar' and group_id='4'"
  "name='foo''bar' and group_id='4'" returns "name='foo''bar' and group_id='4'"
      # File activerecord/lib/active_record/base.rb, line 2269
2269:         def sanitize_sql_for_conditions(condition, table_name = quoted_table_name)
2270:           return nil if condition.blank?
2272:           case condition
2273:             when Array; sanitize_sql_array(condition)
2274:             when Hash;  sanitize_sql_hash_for_conditions(condition, table_name)
2275:             else        condition
2276:           end
2277:         end

Sanitizes a hash of attribute/value pairs into SQL conditions for a SET clause.

  { :status => nil, :group_id => 1 }
    # => "status = NULL , group_id = 1"
      # File activerecord/lib/active_record/base.rb, line 2370
2370:         def sanitize_sql_hash_for_assignment(attrs)
2371:  do |attr, value|
2372:             "#{connection.quote_column_name(attr)} = #{quote_bound_value(value)}"
2373:           end.join(', ')
2374:         end
sanitize_sql_hash_for_conditions(attrs, default_table_name = quoted_table_name)

Sanitizes a hash of attribute/value pairs into SQL conditions for a WHERE clause.

  { :name => "foo'bar", :group_id => 4 }
    # => "name='foo''bar' and group_id= 4"
  { :status => nil, :group_id => [1,2,3] }
    # => "status IS NULL and group_id IN (1,2,3)"
  { :age => 13..18 }
    # => "age BETWEEN 13 AND 18"
  { '' => 7 }
    # => "`other_records`.`id` = 7"
  { :other_records => { :id => 7 } }
    # => "`other_records`.`id` = 7"

And for value objects on a composed_of relationship:

  { :address =>"123 abc st.", "chicago") }
    # => "address_street='123 abc st.' and address_city='chicago'"
      # File activerecord/lib/active_record/base.rb, line 2340
2340:         def sanitize_sql_hash_for_conditions(attrs, default_table_name = quoted_table_name)
2341:           attrs = expand_hash_conditions_for_aggregates(attrs)
2343:           conditions = do |attr, value|
2344:             table_name = default_table_name
2346:             unless value.is_a?(Hash)
2347:               attr = attr.to_s
2349:               # Extract table name from qualified attribute names.
2350:               if attr.include?('.')
2351:                 attr_table_name, attr = attr.split('.', 2)
2352:                 attr_table_name = connection.quote_table_name(attr_table_name)
2353:               else
2354:                 attr_table_name = table_name
2355:               end
2357:               attribute_condition("#{attr_table_name}.#{connection.quote_column_name(attr)}", value)
2358:             else
2359:               sanitize_sql_hash_for_conditions(value, connection.quote_table_name(attr.to_s))
2360:             end
2361:           end.join(' AND ')
2363:           replace_bind_variables(conditions, expand_range_bind_variables(attrs.values))
2364:         end
with_exclusive_scope(method_scoping = {}, &block)

Works like with_scope, but discards any nested properties.

      # File activerecord/lib/active_record/base.rb, line 2193
2193:         def with_exclusive_scope(method_scoping = {}, &block)
2194:           with_scope(method_scoping, :overwrite, &block)
2195:         end
with_scope(method_scoping = {}, action = :merge) {|| ...}

Scope parameters to method calls within the block. Takes a hash of method_name => parameters hash. method_name may be :find or :create. :find parameters may include the :conditions, :joins, :include, :offset, :limit, and :readonly options. :create parameters are an attributes hash.

  class Article < ActiveRecord::Base
    def self.create_with_scope
      with_scope(:find => { :conditions => "blog_id = 1" }, :create => { :blog_id => 1 }) do
        find(1) # => SELECT * from articles WHERE blog_id = 1 AND id = 1
        a = create(1)
        a.blog_id # => 1

In nested scopings, all previous parameters are overwritten by the innermost rule, with the exception of :conditions, :include, and :joins options in :find, which are merged.

:joins options are uniqued so multiple scopes can join in the same table without table aliasing problems. If you need to join multiple tables, but still want one of the tables to be uniqued, use the array of strings format for your joins.

  class Article < ActiveRecord::Base
    def self.find_with_scope
      with_scope(:find => { :conditions => "blog_id = 1", :limit => 1 }, :create => { :blog_id => 1 }) do
        with_scope(:find => { :limit => 10 })
          find(:all) # => SELECT * from articles WHERE blog_id = 1 LIMIT 10
        with_scope(:find => { :conditions => "author_id = 3" })
          find(:all) # => SELECT * from articles WHERE blog_id = 1 AND author_id = 3 LIMIT 1

You can ignore any previous scopings by using the with_exclusive_scope method.

  class Article < ActiveRecord::Base
    def self.find_with_exclusive_scope
      with_scope(:find => { :conditions => "blog_id = 1", :limit => 1 }) do
        with_exclusive_scope(:find => { :limit => 10 })
          find(:all) # => SELECT * from articles LIMIT 10

Note: the +:find+ scope also has effect on update and deletion methods, like update_all and delete_all.

      # File activerecord/lib/active_record/base.rb, line 2132
2132:         def with_scope(method_scoping = {}, action = :merge, &block)
2133:           method_scoping = method_scoping.method_scoping if method_scoping.respond_to?(:method_scoping)
2135:           # Dup first and second level of hash (method and params).
2136:           method_scoping = method_scoping.inject({}) do |hash, (method, params)|
2137:             hash[method] = (params == true) ? params : params.dup
2138:             hash
2139:           end
2141:           method_scoping.assert_valid_keys([ :find, :create ])
2143:           if f = method_scoping[:find]
2144:             f.assert_valid_keys(VALID_FIND_OPTIONS)
2145:             set_readonly_option! f
2146:           end
2148:           # Merge scopings
2149:           if [:merge, :reverse_merge].include?(action) && current_scoped_methods
2150:             method_scoping = current_scoped_methods.inject(method_scoping) do |hash, (method, params)|
2151:               case hash[method]
2152:                 when Hash
2153:                   if method == :find
2154:                     (hash[method].keys + params.keys).uniq.each do |key|
2155:                       merge = hash[method][key] && params[key] # merge if both scopes have the same key
2156:                       if key == :conditions && merge
2157:                         if params[key].is_a?(Hash) && hash[method][key].is_a?(Hash)
2158:                           hash[method][key] = merge_conditions(hash[method][key].deep_merge(params[key]))
2159:                         else
2160:                           hash[method][key] = merge_conditions(params[key], hash[method][key])
2161:                         end
2162:                       elsif key == :include && merge
2163:                         hash[method][key] = merge_includes(hash[method][key], params[key]).uniq
2164:                       elsif key == :joins && merge
2165:                         hash[method][key] = merge_joins(params[key], hash[method][key])
2166:                       else
2167:                         hash[method][key] = hash[method][key] || params[key]
2168:                       end
2169:                     end
2170:                   else
2171:                     if action == :reverse_merge
2172:                       hash[method] = hash[method].merge(params)
2173:                     else
2174:                       hash[method] = params.merge(hash[method])
2175:                     end
2176:                   end
2177:                 else
2178:                   hash[method] = params
2179:               end
2180:               hash
2181:             end
2182:           end
2184:           self.scoped_methods << method_scoping
2185:           begin
2186:             yield
2187:           ensure
2188:             self.scoped_methods.pop
2189:           end
2190:         end
Public Instance methods

Returns true if the comparison_object is the same object, or is of the same type and has the same id.

      # File activerecord/lib/active_record/base.rb, line 2857
2857:       def ==(comparison_object)
2858:         comparison_object.equal?(self) ||
2859:           (comparison_object.instance_of?(self.class) &&
2860:    == id &&
2861:             !comparison_object.new_record?)
2862:       end

Returns the value of the attribute identified by attr_name after it has been typecast (for example, "2004-12-12" in a data column is cast to a date object, like, 12, 12)). (Alias for the protected read_attribute method).

      # File activerecord/lib/active_record/base.rb, line 2755
2755:       def [](attr_name)
2756:         read_attribute(attr_name)
2757:       end
[]=(attr_name, value)

Updates the attribute identified by attr_name with the specified value. (Alias for the protected write_attribute method).

      # File activerecord/lib/active_record/base.rb, line 2761
2761:       def []=(attr_name, value)
2762:         write_attribute(attr_name, value)
2763:       end

Returns an inspect-like string for the value of the attribute attr_name. String attributes are elided after 50 characters, and Date and Time attributes are returned in the :db format. Other attributes return the value of inspect without modification.

  person = Person.create!(:name => "David Heinemeier Hansson " * 3)

  # => '"David Heinemeier Hansson David Heinemeier Hansson D..."'

  # => '"2009-01-12 04:48:57"'
      # File activerecord/lib/active_record/base.rb, line 2822
2822:       def attribute_for_inspect(attr_name)
2823:         value = read_attribute(attr_name)
2825:         if value.is_a?(String) && value.length > 50
2826:           "#{value[0..50]}...".inspect
2827:         elsif value.is_a?(Date) || value.is_a?(Time)
2828:           %("#{value.to_s(:db)}")
2829:         else
2830:           value.inspect
2831:         end
2832:       end

Returns an array of names for the attributes available on this object sorted alphabetically.

      # File activerecord/lib/active_record/base.rb, line 2847
2847:       def attribute_names
2848:         @attributes.keys.sort
2849:       end

Returns true if the specified attribute has been set by the user or by a database load and is neither nil nor empty? (the latter only applies to objects that respond to empty?, most notably Strings).

      # File activerecord/lib/active_record/base.rb, line 2836
2836:       def attribute_present?(attribute)
2837:         value = read_attribute(attribute)
2838:         !value.blank?
2839:       end

Returns a hash of all the attributes with their names as keys and the values of the attributes as values.

      # File activerecord/lib/active_record/base.rb, line 2795
2795:       def attributes
2796:         attrs = {}
2797:         attribute_names.each { |name| attrs[name] = read_attribute(name) }
2798:         attrs
2799:       end
attributes=(new_attributes, guard_protected_attributes = true)

Allows you to set all the attributes at once by passing in a hash with keys matching the attribute names (which again matches the column names).

If guard_protected_attributes is true (the default), then sensitive attributes can be protected from this form of mass-assignment by using the attr_protected macro. Or you can alternatively specify which attributes can be accessed with the attr_accessible macro. Then all the attributes not included in that won‘t be allowed to be mass-assigned.

  class User < ActiveRecord::Base
    attr_protected :is_admin

  user =
  user.attributes = { :username => 'Phusion', :is_admin => true }
  user.username   # => "Phusion"
  user.is_admin?  # => false

  user.send(:attributes=, { :username => 'Phusion', :is_admin => true }, false)
  user.is_admin?  # => true
      # File activerecord/lib/active_record/base.rb, line 2785
2785:       def attributes=(new_attributes, guard_protected_attributes = true)
2786:         return if new_attributes.nil?
2787:         attributes = new_attributes.dup
2788:         attributes.stringify_keys!
2790:         attributes = remove_attributes_protected_from_mass_assignment(attributes) if guard_protected_attributes
2791:         assign_attributes(attributes) if attributes and attributes.any?
2792:       end

Returns a hash of attributes before typecasting and deserialization.

      # File activerecord/lib/active_record/base.rb, line 2802
2802:       def attributes_before_type_cast
2803:         self.attribute_names.inject({}) do |attrs, name|
2804:           attrs[name] = read_attribute_before_type_cast(name)
2805:           attrs
2806:         end
2807:       end

Returns an instance of the specified klass with the attributes of the current record. This is mostly useful in relation to single-table inheritance structures where you want a subclass to appear as the superclass. This can be used along with record identification in Action Pack to allow, say, Client < Company to do something like render :partial => @client.becomes(Company) to render that instance using the companies/company partial instead of clients/client.

Note: The new instance will share a link to the same attributes as the original class. So any change to the attributes in either instance will affect the other.

      # File activerecord/lib/active_record/base.rb, line 2652
2652:       def becomes(klass)
2653: do |became|
2654:           became.instance_variable_set("@attributes", @attributes)
2655:           became.instance_variable_set("@attributes_cache", @attributes_cache)
2656:           became.instance_variable_set("@new_record", new_record?)
2657:         end
2658:       end

Returns a cache key that can be used to identify this record.

Examples     # => "products/new"
  Product.find(5).cache_key # => "products/5" (updated_at not available)
  Person.find(5).cache_key  # => "people/5-20071224150000" (updated_at available)
      # File activerecord/lib/active_record/base.rb, line 2534
2534:       def cache_key
2535:         case
2536:         when new_record?
2537:           "#{self.class.model_name.cache_key}/new"
2538:         when timestamp = self[:updated_at]
2539:           "#{self.class.model_name.cache_key}/#{id}-#{timestamp.to_s(:number)}"
2540:         else
2541:           "#{self.class.model_name.cache_key}/#{id}"
2542:         end
2543:       end

Returns a clone of the record that hasn‘t been assigned an id yet and is treated as a new record. Note that this is a "shallow" clone: it copies the object‘s attributes only, not its associations. The extent of a "deep" clone is application-specific and is therefore left to the application to implement according to its need.

      # File activerecord/lib/active_record/base.rb, line 2637
2637:       def clone
2638:         attrs = clone_attributes(:read_attribute_before_type_cast)
2639:         attrs.delete(self.class.primary_key)
2640:         record =
2641:         record.send :instance_variable_set, '@attributes', attrs
2642:         record
2643:       end

Returns the column object for the named attribute.

      # File activerecord/lib/active_record/base.rb, line 2852
2852:       def column_for_attribute(name)
2853:         self.class.columns_hash[name.to_s]
2854:       end

Returns the connection currently associated with the class. This can also be used to "borrow" the connection to do database work that isn‘t easily done without going straight to SQL.

    # File activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 19
19:     def connection
20:       self.class.connection
21:     end
decrement(attribute, by = 1)

Initializes attribute to zero if nil and subtracts the value passed as by (default is 1). The decrement is performed directly on the underlying attribute, no setter is invoked. Only makes sense for number-based attributes. Returns self.

      # File activerecord/lib/active_record/base.rb, line 2709
2709:       def decrement(attribute, by = 1)
2710:         self[attribute] ||= 0
2711:         self[attribute] -= by
2712:         self
2713:       end
decrement!(attribute, by = 1)

Wrapper around decrement that saves the record. This method differs from its non-bang version in that it passes through the attribute setter. Saving is not subjected to validation checks. Returns true if the record could be saved.

      # File activerecord/lib/active_record/base.rb, line 2719
2719:       def decrement!(attribute, by = 1)
2720:         decrement(attribute, by).update_attribute(attribute, self[attribute])
2721:       end

Deletes the record in the database and freezes this instance to reflect that no changes should be made (since they can‘t be persisted). Returns the frozen instance.

The row is simply removed with a SQL DELETE statement on the record‘s primary key, and no callbacks are executed.

To enforce the object‘s before_destroy and after_destroy callbacks, Observer methods, or any :dependent association options, use destroy.

      # File activerecord/lib/active_record/base.rb, line 2611
2611:       def delete
2612:         self.class.delete(id) unless new_record?
2613:         @destroyed = true
2614:         freeze
2615:       end

Deletes the record in the database and freezes this instance to reflect that no changes should be made (since they can‘t be persisted).

      # File activerecord/lib/active_record/base.rb, line 2619
2619:       def destroy
2620:         unless new_record?
2621:           connection.delete(
2622:             "DELETE FROM #{self.class.quoted_table_name} " +
2623:             "WHERE #{connection.quote_column_name(self.class.primary_key)} = #{quoted_id}",
2624:             "#{} Destroy"
2625:           )
2626:         end
2628:         @destroyed = true
2629:         freeze
2630:       end

Returns true if the record has been destroyed.

      # File activerecord/lib/active_record/base.rb, line 2886
2886:       def destroyed?
2887:         @destroyed
2888:       end

Delegates to ==

      # File activerecord/lib/active_record/base.rb, line 2865
2865:       def eql?(comparison_object)
2866:         self == (comparison_object)
2867:       end

Freeze the attributes hash such that associations are still accessible, even on destroyed records.

      # File activerecord/lib/active_record/base.rb, line 2876
2876:       def freeze
2877:         @attributes.freeze; self
2878:       end

Returns true if the attributes hash has been frozen.

      # File activerecord/lib/active_record/base.rb, line 2881
2881:       def frozen?
2882:         @attributes.frozen?
2883:       end

Returns true if the given attribute is in the attributes hash

      # File activerecord/lib/active_record/base.rb, line 2842
2842:       def has_attribute?(attr_name)
2843:         @attributes.has_key?(attr_name.to_s)
2844:       end

Delegates to id in order to allow two records of the same type and id to work with something like:

  [ Person.find(1), Person.find(2), Person.find(3) ] & [ Person.find(1), Person.find(4) ] # => [ Person.find(1) ]
      # File activerecord/lib/active_record/base.rb, line 2871
2871:       def hash
2872:         id.hash
2873:       end

A model instance‘s primary key is always available as whether you name it the default ‘id’ or set it to something else.

      # File activerecord/lib/active_record/base.rb, line 2490
2490:       def id
2491:         attr_name = self.class.primary_key
2492:         column = column_for_attribute(attr_name)
2494:         self.class.send(:define_read_method, :id, attr_name, column)
2495:         # now that the method exists, call it
2496:         self.send attr_name.to_sym
2498:       end

Sets the primary ID.

      # File activerecord/lib/active_record/base.rb, line 2554
2554:       def id=(value)
2555:         write_attribute(self.class.primary_key, value)
2556:       end
increment(attribute, by = 1)

Initializes attribute to zero if nil and adds the value passed as by (default is 1). The increment is performed directly on the underlying attribute, no setter is invoked. Only makes sense for number-based attributes. Returns self.

      # File activerecord/lib/active_record/base.rb, line 2692
2692:       def increment(attribute, by = 1)
2693:         self[attribute] ||= 0
2694:         self[attribute] += by
2695:         self
2696:       end
increment!(attribute, by = 1)

Wrapper around increment that saves the record. This method differs from its non-bang version in that it passes through the attribute setter. Saving is not subjected to validation checks. Returns true if the record could be saved.

      # File activerecord/lib/active_record/base.rb, line 2702
2702:       def increment!(attribute, by = 1)
2703:         increment(attribute, by).update_attribute(attribute, self[attribute])
2704:       end

Returns the contents of the record as a nicely formatted string.

      # File activerecord/lib/active_record/base.rb, line 2902
2902:       def inspect
2903:         attributes_as_nice_string = self.class.column_names.collect { |name|
2904:           if has_attribute?(name) || new_record?
2905:             "#{name}: #{attribute_for_inspect(name)}"
2906:           end
2907:         }.compact.join(", ")
2908:         "#<#{self.class} #{attributes_as_nice_string}>"
2909:       end

Returns true if this object hasn‘t been saved yet — that is, a record for the object doesn‘t exist yet; otherwise, returns false.

      # File activerecord/lib/active_record/base.rb, line 2559
2559:       def new_record?
2560:         @new_record || false
2561:       end

Marks this record as read only.

      # File activerecord/lib/active_record/base.rb, line 2897
2897:       def readonly!
2898:         @readonly = true
2899:       end

Returns true if the record is read only. Records loaded through joins with piggy-back attributes will be marked as read only since they cannot be saved.

      # File activerecord/lib/active_record/base.rb, line 2892
2892:       def readonly?
2893:         defined?(@readonly) && @readonly == true
2894:       end
reload(options = nil)

Reloads the attributes of this object from the database. The optional options argument is passed to find when reloading so you may do e.g. record.reload(:lock => true) to reload the same record with an exclusive row lock.

      # File activerecord/lib/active_record/base.rb, line 2744
2744:       def reload(options = nil)
2745:         clear_aggregation_cache
2746:         clear_association_cache
2747:         @attributes.update(self.class.send(:with_exclusive_scope) { self.class.find(, options) }.instance_variable_get('@attributes'))
2748:         @attributes_cache = {}
2749:         self
2750:       end
save(perform_validation = true)

Saves the model.

If the model is new a record gets created in the database, otherwise the existing record gets updated.

If perform_validation is true validations run. If any of them fail the action is cancelled and save returns false. If the flag is false validations are bypassed altogether. See ActiveRecord::Validations for more information.

There‘s a series of callbacks associated with save. If any of the before_* callbacks return false the action is cancelled and save returns false. See ActiveRecord::Callbacks for further details.

      # File activerecord/lib/active_record/base.rb, line 2580
2580:       def save
2581:         create_or_update
2582:       end

Saves the model.

If the model is new a record gets created in the database, otherwise the existing record gets updated.

With save! validations always run. If any of them fail ActiveRecord::RecordInvalid gets raised. See ActiveRecord::Validations for more information.

There‘s a series of callbacks associated with save!. If any of the before_* callbacks return false the action is cancelled and save! raises ActiveRecord::RecordNotSaved. See ActiveRecord::Callbacks for further details.

      # File activerecord/lib/active_record/base.rb, line 2597
2597:       def save!
2598:         create_or_update || raise(RecordNotSaved)
2599:       end

Returns a String, which Action Pack uses for constructing an URL to this object. The default implementation returns this record‘s id as a String, or nil if this record‘s unsaved.

For example, suppose that you have a User model, and that you have a map.resources :users route. Normally, user_path will construct a path with the user object‘s ‘id’ in it:

  user = User.find_by_name('Phusion')
  user_path(user)  # => "/users/1"

You can override to_param in your model to make user_path construct a path using the user‘s name instead of the user‘s id:

  class User < ActiveRecord::Base
    def to_param  # overridden

  user = User.find_by_name('Phusion')
  user_path(user)  # => "/users/Phusion"
      # File activerecord/lib/active_record/base.rb, line 2522
2522:       def to_param
2523:         # We can't use alias_method here, because method 'id' optimizes itself on the fly.
2524:         (id = ? id.to_s : nil # Be sure to stringify the id for routes
2525:       end

Assigns to attribute the boolean opposite of attribute?. So if the predicate returns true the attribute will become false. This method toggles directly the underlying value without calling any setter. Returns self.

      # File activerecord/lib/active_record/base.rb, line 2727
2727:       def toggle(attribute)
2728:         self[attribute] = !send("#{attribute}?")
2729:         self
2730:       end

Wrapper around toggle that saves the record. This method differs from its non-bang version in that it passes through the attribute setter. Saving is not subjected to validation checks. Returns true if the record could be saved.

      # File activerecord/lib/active_record/base.rb, line 2736
2736:       def toggle!(attribute)
2737:         toggle(attribute).update_attribute(attribute, self[attribute])
2738:       end
update_attribute(name, value)

Updates a single attribute and saves the record without going through the normal validation procedure. This is especially useful for boolean flags on existing records. The regular update_attribute method in Base is replaced with this when the validations module is mixed in, which it is by default.

      # File activerecord/lib/active_record/base.rb, line 2663
2663:       def update_attribute(name, value)
2664:         send(name.to_s + '=', value)
2665:         save(false)
2666:       end

Updates all the attributes from the passed-in Hash and saves the record. If the object is invalid, the saving will fail and false will be returned.

      # File activerecord/lib/active_record/base.rb, line 2670
2670:       def update_attributes(attributes)
2671:         with_transaction_returning_status(:update_attributes_inside_transaction, attributes)
2672:       end

Updates an object just like Base.update_attributes but calls save! instead of save so an exception is raised if the record is invalid.

      # File activerecord/lib/active_record/base.rb, line 2680
2680:       def update_attributes!(attributes)
2681:         with_transaction_returning_status(:update_attributes_inside_transaction!, attributes)
2682:       end