在ApplicationForm 类中，需要指定ApplicationForms 与'form_questions' 的关系.它还不知道.在您使用 :through 的任何地方，您都需要先告诉它在哪里可以找到该记录.你的其他课程也有同样的问题.

In the ApplicationForm class, you need to specify ApplicationForms's relationship to 'form_questions'. It doesn't know about it yet. Anywhere you use the :through, you need to tell it where to find that record first. Same problem with your other classes.

所以

# application_form.rb
class ApplicationForm < ActiveRecord::Base
  has_many :form_questions
  has_many :questions, :through => :form_questions
end

# question.rb
class Question < ActiveRecord::Base
  belongs_to :section
  has_many :form_questions
  has_many :application_forms, :through => :form_questions
end

# form_question.rb
class FormQuestion < ActiveRecord::Base
  belongs_to :question
  belongs_to :application_form
  belongs_to :question_type
  has_many :form_questions_answers
  has_many :answers, :through => :form_question_answers
end

假设您就是这样设置的.

That is assuming that's how you have it set up.