File: README — Documentation for dwilkie-foreigner (0.3)

Foreigner

Adds limited SQLite support for Matt Higgins Foreigner.

Allows you to do the following in your migration files

t.foreign_key :posts

Which will generate the following SQL:

FOREIGN KEY ("post_id") REFERENCES "posts"(id)

To enforce the constraint use the genfkey tool included with SQLite:

rake db:migrate
sqlite3 db/development.sqlite3
.genfkey --exec

For more info see www.sqlite.org/cvstrac/fileview?f=sqlite/tool/genfkey.README

Installation

Install as a plugin:

ruby script/plugin install git://github.com/dwilkie/foreigner.git

Install as a gem by adding the following to environment.rb:

config.gem "dwilkie-foreigner", :lib => "foreigner"

API

t.foreign_key(options)
foreign_keys(table_name)

Since SQLite does not have complete ALTER TABLE support
you cannot use the following for an SQLite database

add_foreign_key(from_table, to_table, options)
remove_foreign_key(from_table, options)

Example

The most common use of foreign keys is to reference a table that a model belongs to. For example, given the following model:

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:

t.foreign_key :posts

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

t.foreign_key(:posts, :column => 'article_id')

schema.rb

Similar to indexes, the foreign keys in your database are automatically dumped to schema.rb. This allows you to use foreign keys without fighting Rails!