Polymorphic association with has_one, can't create through association

Question

I've got a polymorphic association with a has_one and it gives me an error when trying to create through association.

class User < ActiveRecord::Base
  belongs_to :userable, polymorphic: true
end

class Student < ActiveRecord::Base
  attr_accessible :gender, :description, :dob
  has_one :user, :as => :userable
end

If I try to do:

s = Student.new
s.user.create

I get and error Undefined method create for 'nil'

But! If i change the association to has_many users then I can now preform the same lines above.

Can anyone explain why this is happening? Thanks!

Answer 1

The problem is that user is nil since you haven't assigned a value to it. You should use something like:

s.build_user(...)

or

s.create_user(...)