While working on a Rails 4 application, I came across a new addition to migrations add_reference. add_reference makes it easier to create migrations for foreign keys.

Rails 3

In Rails 3, to add a foreign key and an index you would write a migration like this:

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class AddUserToBooks < ActiveRecord::Migration
  def change
    add_column :books, :user_id, :integer
    add_index  :books, :user_id
  end
end

It requires two method calls, one to add the user_id column to the Books table, and another to add an index to user_id.

Rails 4

In Rails 4, you can accomplish the same thing with add_reference:

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class AddUserToBooks < ActiveRecord::Migration
  def change
    add_reference :books, :user, index: true
  end
end

While it isn’t a major change, it further illustrates the foundation that Ruby was built upon.

“Ruby is designed to make programmers happy.” - Yukihiro Matsumoto