Rails 3 migrations: Adding reference column?

Question

If I create a new rails 3 migration with (for example)

rails g migration tester title:tester user:references

, everything works fine...howe

Answer 1

For Rails 4

The generator accepts column type as references (also available as belongs_to).

This migration will create a user_id column and appropriate index:

$ rails g migration AddUserRefToProducts user:references 

generates:

class AddUserRefToProducts < ActiveRecord::Migration
  def change
    add_reference :products, :user, index: true
  end
end

http://guides.rubyonrails.org/active_record_migrations.html#creating-a-standalone-migration

For Rails 3

Helper is called references (also available as belongs_to).

This migration will create a category_id column of the appropriate type. Note that you pass the model name, not the column name. Active Record adds the _id for you.

change_table :products do |t|
  t.references :category
end

If you have polymorphic belongs_to associations then references will add both of the columns required:

change_table :products do |t|
  t.references :attachment, :polymorphic => {:default => 'Photo'}
end

Will add an attachment_id column and a string attachment_type column with a default value of Photo.

http://guides.rubyonrails.org/v3.2.21/migrations.html#creating-a-standalone-migration