Allows programmers to programmatically define a schema in a portable DSL. This means you can define tables, indexes, etc. without using SQL directly, so your applications can more easily support multiple databases.


  ActiveRecord::Schema.define do
    create_table :authors do |t|
      t.string :name, :null => false

    add_index :authors, :name, :unique

    create_table :posts do |t|
      t.integer :author_id, :null => false
      t.string :subject
      t.text :body
      t.boolean :private, :default => false

    add_index :posts, :author_id

ActiveRecord::Schema is only supported by database adapters that also support migrations, the two features being very similar.

Public Class methods
define(info={}, &block)

Eval the given block. All methods available to the current connection adapter are available within the block, so you can easily use the database definition DSL to build up your schema (create_table, add_index, etc.).

The info hash is optional, and if given is used to define metadata about the current schema (currently, only the schema‘s version):

  ActiveRecord::Schema.define(:version => 20380119000001) do
    # File activerecord/lib/active_record/schema.rb, line 46
46:     def self.define(info={}, &block)
47:       instance_eval(&block)
49:       unless info[:version].blank?
50:         initialize_schema_migrations_table
51:         assume_migrated_upto_version(info[:version], migrations_path)
52:       end
53:     end
    # File activerecord/lib/active_record/schema.rb, line 31
31:     def self.migrations_path
32:       ActiveRecord::Migrator.migrations_path
33:     end