Nested model creation in rails

Question

I'm playing around with the Rails Console and was wondering why the following code doesn't work:

Question.create(body: "Why this does not work?", answer_attributes: {body: "Some Answer"})

It's weird cause when I do this:

question = Question.new(body: "Why this does not work?", answer_attributes: {body: "Some Answer"})
question.answer

I get something that looks like this:

=> #<Answer id: nil, body: "Some Answer", question_id: nil, created_at: nil, updated_at: nil>

It seems that the answer object is associated with the question object...

Now if I try to save the object, it doesn't work:

question.save

I get this:

 => false

When I call .errors on it I get this:

question.errors
@messages={:"answer.question_id"=>["can't be blank"]}>

Both objects are new so it's kinda normal the question object doesn't have an id.

I know I could create the answer object by creating a question first and then call update_attributes on it... Or simply by creating a question and then calling answers.build on it...

My question is... Is there a way for a child model to get its parent's id upon creation?

Oh and if you're wondering, I do have a validation that requires an answer to have a question_id value.

thx!

Answer 1

I finally found an answer to my question...

I needed to put this code:

:inverse_of => :question

So my question model would look like this:

class Question < ActiveRecord::Base
  has_many :answers, :dependent => :destroy, :inverse_of :question

  accepts_nested_attributes_for :answers
end

My answer model would look like this:

class Answer < ActiveRecord::Base
  belongs_to :question

  validates :question, :presence => true
end