belongs_to through associations

Question

Hi, can someone help me look at this. Getting too tired.

class User
  has_many :questions
  has_many :choices
end

class Question
  belongs_to :user
  has_many :answers
  has_one :choice, :through => :answer
end

class Answer
  belongs_to :question
end

class Choice
  belongs_to :user
  belongs_to :answer
  belongs_to :question, :through => :answer

  validates_uniqueness_of :answer_id, :scope => [ :question_id, :user_id ]
end

I am getting a NameError uninitialized constant User::Choice when I try to do current_user.choices

It works fine, if I don't include the

belongs_to :question, :through => :answer

But I want to use that because I want to be able to do the validates_uniqueness_of

I am probably overlooking something simple. Any help would be appreciated. Thanks!

Answer 1

The has_many :choices creates an association named choices, not choice. Try using current_user.choices instead.

See the ActiveRecord::Associations documentation for information about about the has_many magic.

Answer 2

A belongs_to association cannot have a :through option. You're better off caching the question_id on Choice and adding a unique index to the table (especially because validates_uniqueness_of is prone to race conditions).

If you're paranoid, add a custom validation to Choice that confirms that the answer's question_id matches, but it sounds like the end user should never be given the opportunity to submit data that would create this kind of mismatch.

Answer 3

It sounds like what you want is a User who has many Questions.
The Question has many Answers, one of which is the User's Choice.

Is this what you are after?

I would model something like that along these lines:

class User
  has_many :questions
end

class Question
  belongs_to :user
  has_many   :answers
  has_one    :choice, :class_name => "Answer"

  validates_inclusion_of :choice, :in => lambda { answers }
end

class Answer
  belongs_to :question
end