Selective delete from join tables

Hi,

I'm learning rails and have run into what for me is a difficult problem. I have the following associations with a galleries_pictures and a pictures_questions join table:

class Picture < ActiveRecord::Base   has_and_belongs_to_many :questions   has_and_belongs_to_many :galleries

class Question < ActiveRecord::Base   has_and_belongs_to_many :pictures

class Gallery < ActiveRecord::Base   has_and_belongs_to_many :pictures

In the edit question view, a question and its associated picture(s) can be edited. My problem is, I cannot figure out how to delete the picture in the question and at the same time not delete it from the gallery ie delete the pictures_questions association but not the galleries_pictures association.

The action called from the view deletes the row in both join tables: def destroy     @picture = Picture.find(params[:id])     @picture.destroy

Thanks!

Dave Castellano wrote in post #1110796:

Hi,

I'm learning rails and have run into what for me is a difficult problem. I have the following associations with a galleries_pictures and a pictures_questions join table:

class Picture < ActiveRecord::Base   has_and_belongs_to_many :questions   has_and_belongs_to_many :galleries

class Question < ActiveRecord::Base   has_and_belongs_to_many :pictures

class Gallery < ActiveRecord::Base   has_and_belongs_to_many :pictures

In the edit question view, a question and its associated picture(s) can be edited. My problem is, I cannot figure out how to delete the picture in the question and at the same time not delete it from the gallery ie delete the pictures_questions association but not the galleries_pictures association.

The action called from the view deletes the row in both join tables: def destroy     @picture = Picture.find(params[:id])     @picture.destroy

Thanks!

Here you are destroying the picture object so naturally Rails will manage the associations automatically. What you want to do instead is to delete the association not the actual picture object.

There are a couple of ways to do this. But, you do not wan to use the destroy action on pictures_controller. That action should be used to destroy pictures not associations.

Option 1—Expose the join model and manage the association with standard REST destroy action on the association model:

class Picture < ActiveRecord::Base   has_many :question_pictures   has_many :questions, :through => :question_pictures end

class Question < ActiveRecord::Base   has_many :question_pictures   has_many :pictures, :through => :question_pictures end

class QuestionPicture < ActiveRecord::Base   belongs_to :question   belongs_to :picture end

question_pictures_controller

P.S. None of this code has been tested. Just wrote it by memory.

Thank you. I get it. It worked well with a couple of small tweaks. ...wish I could do that from memory :slight_smile:

Thanks, Dave