t.belongs_to in migration

Question

I was using Ryan Bates's source code for railscasts #141 in order to create a simple shopping cart. In one of the migrations, he lists

class CreateProducts < ActiveRecord::Migration   def self.up     create_table :products do |t|       t.belongs_to :category       t.string :name       t.decimal :price       t.text :description       t.timestamps     end   end    def self.down     drop_table :products   end end 

Here is the Product model:

class Product < ActiveRecord::Base  belongs_to :category end 

What is the t.belongs_to :category line? Is that an alias for t.integer category_id?

Answer 1

The t.belongs_to :category is just a special helper method of rails passing in the association.

If you look in the source code belongs_to is actually an alias of references

Answer 2

$ rails g migration AddUserRefToProducts user:references  

this 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