rails HABTM to has many through

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

The above models are inherited from the base model Exam(using rails STI) and the join table contains two fields: question_id and question_set_id. Now I need to convert this association into has_many through.

I have tried as follows:

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

Please show what you have tried on your own before asking someone to do it for you. — Arslan Ali, Dec 10 '16 at 13:58
I was playing around with class name and foreign_key. But nothing worked for me — Vijith mv, Dec 10 '16 at 14:00
I'm asking for database schema. You can find it here: `db/schema.rb` — Arslan Ali, Dec 10 '16 at 14:11
create_table "question_question_sets", force: :cascade do |t| t.integer "question_id" t.integer "question_set_id" t.datetime "created_at", null: false t.datetime "updated_at", null: false end — Vijith mv, Dec 10 '16 at 14:13

score 2 · Answer 1 · answered Dec 07 '17 at 07:43

Even after editing your models, it's necessary to create a new join table since the previous one (created by habtm) doesn't have and "id" column. As a reference you can follow the steps indicated in http://www.chrisrolle.com/en/blog/migration-path-from-habtm-to-has_many-through

rails HABTM to has many through

1 Answers1