Foreigner

Foreigner introduces a few methods to your migrations for adding and removing foreign key constraints. It also dumps foreign keys to schema.rb.

The following adapters are supported:

Installation

Add the following to your Gemfile:

“by gem ‘foreigner’

“

Foreigner adds two methods to migrations.

(Options are documented in connection_adapters/abstract/schema_definitions.rb):

For example, given the following model:

“by class Comment < ActiveRecord::Base belongs_to :post end

class Post < ActiveRecord::Base has_many :comments, dependent: :delete_all end

“ You should add a foreign key in your migration:

“by add_foreign_key(:comments, :posts)

“he :dependent option can be moved from the has_many definition to the foreign key:

“by add_foreign_key(:comments, :posts, dependent: :delete)

“f the column is named article_id instead of post_id, use the :column option:

“by add_foreign_key(:comments, :posts, column: ‘article_id’)

“ name can be specified for the foreign key constraint:

“by add_foreign_key(:comments, :posts, name: ‘comment_article_foreign_key’)

“he :column and :name options create a foreign key with a custom name. In order to remove it you need to specify :name:

“by remove_foreign_key(:comments, name: ‘comment_article_foreign_key’)

“

Foreigner adds extra methods to create_table and change_table.

Create a new table with a foreign key:

“by create_table :products do |t| t.string :name t.integer :factory_id t.foreign_key :factories end

“dd a missing foreign key to comments:

“by change_table :comments do |t| t.foreign_key :posts, dependent: :delete end

“emove an unwanted foreign key:

“by change_table :comments do |t| t.remove_foreign_key :users end

“

Database-specific options will never be supported by foreigner. You can add them using :options:

“by add_foreign_key(:comments, :posts, options: ‘ON UPDATE DEFERRED’)

“