允许用户使用accepting_nested_attributes_for选择正确答案？

Question

我有轨关系：

class Quiz < ActiveRecord::Base 
    has_many :questions, dependent: :destroy 
    accepts_nested_attributes_for :questions, 
          reject_if: proc { |a| a[:content].blank? }, 
          allow_destroy: true 
end 

class Question < ActiveRecord::Base 
    belongs_to :quiz 
    has_many :answers, dependent: :destroy 
    accepts_nested_attributes_for :answers, 
           reject_if: proc { |a| a[:content].blank? }, 
           allow_destroy: true 
end 

class Answer < ActiveRecord::Base 
    belongs_to :question 
end 

怎样的结构模型，所以当用户在测验＃编辑或测验＃新的，他们可以选择哪个答案（含单选按钮）为正确答案？

Answer 1

在answers表中，添加名为'is_correct_answer'的附加属性，该属性仅适用于一个组合。