create_join_table

activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb

@@ -1,3 +1,4 @@
+require 'active_support/core_ext/array/extract_options'
 require 'active_support/deprecation/reporting'
 require 'active_record/schema_migration'
 
@@ -170,6 +171,20 @@ def create_table(table_name, options = {})
         execute create_sql
       end
 
+      # Creates a new join table.
+      def create_join_table(*table_name_or_options)
+        table_name, from, to, options = parse_arguments(table_name_or_options)
+
+        create_table(table_name, options.merge(:id => false)) do |t|
+          t.references from, to, :null => false
+        end
+
+        if options.delete(:index)
+          add_index table_name, "#{from}_id"
+          add_index table_name, "#{to}_id"
+        end
+      end
+
       # A block for changing columns in +table+.
       #
       # === Example
@@ -256,6 +271,12 @@ def drop_table(table_name)
         execute "DROP TABLE #{quote_table_name(table_name)}"
       end
 
+      # Drops a join table from the database.
+      def drop_join_table(*table_name_or_options)
+        table_name, _ = parse_arguments(table_name_or_options)
+        drop_table table_name
+      end
+
       # Adds a new column to the named table.
       # See TableDefinition#column for details of the options you can use.
       def add_column(table_name, column_name, type, options = {})
@@ -571,6 +592,23 @@ def columns_for_remove(table_name, *column_names)
           column_names.map {|column_name| quote_column_name(column_name) }
         end
 
+        def extract_references(options)
+          [options.delete(:tie), options.delete(:to)].sort
+        end
+
+        def join_table_name(from, to)
+          "#{from.to_s.pluralize}_#{to.to_s.pluralize}"
+        end
+
+        def parse_arguments(table_name_or_options)
+          options = table_name_or_options.extract_options!
+
+          from, to   = extract_references(options)
+          table_name = table_name_or_options.empty? ? join_table_name(from, to) : table_name_or_options.first
+
+          [table_name, from, to, options]
+        end
+
       private
       def table_definition
         TableDefinition.new(self)

activerecord/test/cases/migration/create_join_table_test.rb

@@ -0,0 +1,64 @@
+require "cases/migration/helper"
+
+module ActiveRecord
+  class Migration
+    class CreateJoinTableTest < ActiveRecord::TestCase
+      include ActiveRecord::Migration::TestHelper
+
+      self.use_transactional_fixtures = false
+
+      def setup
+        super
+      end
+
+      def test_create_join_table
+        con = connection
+
+        create_join_table :tie => :person, :to => :group
+
+        table_name = "groups_people"
+        assert con.table_exists?(table_name)
+
+        columns = con.columns(table_name)
+        assert !columns.find { |c| c.name == "group_id" }.null
+        assert !columns.find { |c| c.name == "person_id" }.null
+
+        assert !con.index_name_exists?(table_name, "index_groups_people_on_group_id", false)
+        assert !con.index_name_exists?(table_name, "index_groups_people_on_person_id", false)
+      ensure
+        drop_join_table :tie => :person, :to => :group
+      end
+
+      def test_create_join_table_with_index
+        con = connection
+
+        create_join_table :tie => :person, :to => :group, :index => true
+
+        table_name = "groups_people"
+        assert con.index_name_exists?(table_name, "index_groups_people_on_group_id",  false)
+        assert con.index_name_exists?(table_name, "index_groups_people_on_person_id", false)
+      ensure
+        drop_join_table :tie => :person, :to => :group
+      end
+
+      def test_create_join_table_with_table_name_and_options
+        table_name = "habtm"
+        create_join_table table_name, :tie => :person, :to => :group
+        assert connection.table_exists?(table_name)
+      ensure
+        drop_join_table table_name
+      end
+
+      private
+
+      def create_join_table(*args)
+        connection.create_join_table(*args)
+      end
+
+      def drop_join_table(*args)
+        connection.drop_join_table(*args)
+      end
+
+    end
+  end
+end