Rails, what is the best way to link two models and create one before another

Question

I've two models:

class User < ActiveRecord::Base
  before_create :add_address
  has_one :address


  def add_address
    self.address_id ||= Address.generate_new.id
  end
end

And

class Address < ActiveRecord::Base
  belongs_to :user

  def self.generate_new
    new_address = # some code generating UUID

    Address.create!({address: new_address})
  end
end

But when I create User, it saves address, but user_id didn't show on the Address model. I don't want to update Address after creating the User. Maybe I do smth not in a rails way?

Answer 1

But when I create User, it saves address, but user_id didn't show on the Address model.

The reason is your way to create new address is incorrect.

The correct way to build a new Address instance is through associated model User.

@address = @user.address.new("some params")
@address.save

In this way the instance address will have user_id inside automatically.

Two things more:

1. You don't need another generate_new method, if the method does nothing but duplicate the functionality of save, create.

2. Optionally you can validate the presence of user_id in Address model, to ensure user_id is always valid before creating the Address object. It's optional because you can also ensure this as above

   class Address < ActiveRecord::Base
     belongs_to :user
     validates_associated :user
   end