属于_通过协会(belongs_to through associations)

 鉴于以下关联，我需要参考Choice所附的Question 。 我一直在尝试使用belongs_to :question, through: :answer来执行此操作。 
 
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
 
 我正进入（状态 
 
 
 
 NameError未初始化常量User::Choice 
 
 
 当我尝试做current_user.choices 
 
 它工作正常，如果我不包括 
 
belongs_to :question, :through => :answer
 
 但是我想使用它，因为我想要能够执行validates_uniqueness_of 
 
 我可能忽略了一些简单的东西。 任何帮助将不胜感激。 

Given the following associations, I need to reference the Question that a Choice is attached through from the Choice model. I have been attempting to use belongs_to :question, through: :answer to perform this action.
 
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
 
 
 
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.

原文：https://stackoverflow.com/questions/4021322