Adding a Model Reference to existing Rails model

Question

I\'d like to know the \"proper\" way to approach adding a relation between two existing classes in Rails 3.

Given existing models: Clown & Rabbit

I\

Answer 1

If you are using edge rails (4.0) you can use:

rails generate migration AddAddressRefToContacts address:references

As you can see by the docs.

Answer 2

I'm not sure where you got this idea, but there is no (and never has been) such syntax to do what you want with add_column. To get the behavior you want, you'd have to do t.refences :clown, as you stated. In the background this will call: @base.add_column(@table_name, "#{col}_id", :integer, options).

See here.

EDIT:

I think I can see the source of your confusion. You saw the method call t.reference and assumed it was a datatype because calls such as t.integer and t.string exist, and those are datatypes. That's wrong. Reference isn't a datatype, it's just simply the name of a method, similar to t.rename is.

Answer 3

After you set belongs_to in Rabbit, and has_many in Clown, you can do a migration with:

add_column :rabbit, :clown_id, :integer

EDIT: See Paulo's answer below for a more updated answer (Rails 4+)