Dave C. 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
def destroy
question_picture = QuestionPicture.find(params[:id])
question_picture.destroy
end
Option 2—Add an additional RESTful action to questions_controller
config/routes.rb
resources :questions do
delete ‘remove_picture’, :on => :member
end
questions_controller.rb
def remove_picture
question = Question.find(:id)
picture = question.pictures.find(params[:picture_id])
question.pictures.delete(picture)
end
Example URL:
DELETE: http://example.com/galleries/1/remove_picture/?picture_id=1
P.S. None of this code has been tested. Just wrote it by memory.
