Doesn't seem to work with "has_many ... :through "

[fokcep]

it's trying to load id of the association in the target object instead of association.

Looks like a bug

[moiristo]

There are tests for hasmany through relations that pass, so could you be more specific? Which version of rails are you using? A failing test would be helpful (or some sample code to exemplify the issue).

[fokcep]

Rails 3.2.11 Ruby 1.9.3-p374

Example of the problem

Student.rb

has_many :subjects, :through => :student_assignments
has_many :student_assignments, :dependent => :destroy

Subject

has_many :students, :through => :student_assignments
has_many :student_assignments, :dependent => :destroy

StudentAssignment

belongs_to :subject
belongs_to :student

---

Then

Student.first.subjects.size

2

(Student.first.dup :include => [:student_assignments]).subjects.size

0

---

Or am I missing something obvious?

Thanks

[moiristo]

Not sure yet. I'll look into it.

[moiristo]

Hold on, I think you should simply include the subjects instead of the join-table. Try

Student.first.dup(:include => :subjects).subjects.size

Does that work for you? I think it doesn't work in your case because you don't include the associations in student_assignments. This should work too:

Student.first.dup(:include => { :student_assignments => :subject }).subjects.size

[fokcep]

I've tried that too

i.e.

Student.first.dup(:include => :subjects).subjects.size

NoMethodError: undefined method `subject_id=' for #<Subject .....

and

Student.first.dup(:include => { :student_assignments => :subject }).subjects.size

still empty

[moiristo]

Ok, thanks for the bugreport. I'll try to reproduce and fix the issue shortly.

[moiristo]

I've added a test that reproduces the error. Unfortunately, it's trickier then I thought. It is easy to set the association itself, but it's hard to find and set the reverse association (students) on the newly created subjects. For now, I recommend that you stick to the method:

Student.first.dup(:include => :student_assignments) # will create assignments with existing subjects
Student.first.dup(:include => { :student_assignments => :subject }) # will create new subjects

This will not set the 'subjects' association directly, so in that case you'll have to do something like:

Student.first.dup(:include => { :student_assignments => :subject }).student_assignments.map(&:subject)

After saving the student dup the subjects association will be reloaded, therefore it is only a problem before save.

[fokcep]

Thanks for looking into this. I've used something like this as a workaround. Please let me know when/if you fix it in future.

[tristanoneil]

:+1: Also ran into this issue. Worked around it but would be awesome if you could specify either the join model or associated model to clone a has_many :through.

[moiristo]

Fixed it in master, the test described in this issue now passes. Could you please verify that it works properly now?

[tristanoneil]

Just tested it and it does now work! Just including the through association like:

Student.first.dup(:include => :subjects)

[tristanoneil]

:shipit: Maybe we can get a release for this?

[moiristo]

Sure. Done! (1.5.2)