導軌HABTM到有許多通過

Question

class QuestionSet 
    has_and_belongs_to_many :questions, 
         class_name: 'Exam', 
         join_table: 'question_question_sets', 
         foreign_key: 'question_set_id', 
         association_foreign_key: 'question_id' 

end 

class Question 
    has_and_belongs_to_many :question_sets, 
         class_name: 'Exam', 
         join_table: 'question_question_sets', 
         foreign_key: 'question_id', 
         association_foreign_key: 'question_set_id' 

end 

上述型號從基模型Exam繼承（使用導軌STI）和連接表包含兩個字段：question_id和question_set_id。現在我需要將此關聯轉換爲has_many through。

我已經試過如下：

class QuestionQuestionSet 
    has_many :questions 
    has_many :question_sets 
end 

class Question 
    has_many :question_question_sets, foreign_key: :question_id 
    has_many :question_sets, through: :question_question_sets 
end 

class QuestionSet 
    has_many :question_question_sets, foreign_key: :question_set_id 
    has_many :questions, through: :question_question_sets 
end 

Answer 1

即使編輯模式後，有必要創建一個新的連接表，因爲前一個（由HABTM創建）並沒有和「ID」列。 作爲參考，您可以按照http://www.chrisrolle.com/en/blog/migration-path-from-habtm-to-has_many-through