Polymorphic has_many through association causes nil in join table about rails

[gnufied]

I think the only hope of getting this fixed is, if you can attach a some minimum code that we can run locally and reproduce the problem.

[larsar]

I created a minimal rails example project with a readme file explaining how to reproduce the problem:

git://github.com/larsar/rails-issue-403.git

[josevalim]

Thanks @larsar and @gnufied. Can any of the several contributors now isolate the issue from the minimal rails app to a test case in Rails? This would help us a lot in moving on and fixing the issue. ❤️

[gnufied]

On having a look at the sample code, this is not a bug. The problems with code:

1. Following code is wrong and will not work

has_many :deliveries, :as => :notifiable
has_many :members, :through => :deliveries, :source => :notifiable, :source_type => "Member"

Because when you will say notification.members it will create the join with where condition deliveries.notifiable_id=1 AND deliveries.notifiable_type = 'Notification' . Clearly thats not what you want.

1. When you are creating deliveries indirectly via notification.members << member , it WILL set notifiable_id and notifiable_type correctly in deliveries table, but AR has no way of knowing that you want to set notification_id in deliveries table as well. It is impossible, you will have to set that yourself.

   In other words, you are expecting too much from Rails here. :)

[josevalim]

Ok, closing. Thanks @gnufied.

[larsar]

Thanks for taking the time to look at this. I'll have to let it sink in and try another solution then. :)