Linked_to isn't working with different classes (and rails 4?)

[fonji]

Hello!
First of all: this issue concerns the links branch. Please have a look at the corresponding issue #13 if you need more information.

An error is raised when I try to use linked_to objects using another class.

Some background first
I work in healthcare research. In the disorders classifications, a disorder has multiple children (to narrow the diagnosis) and multiple parents (multiple path may lead you to the same disorder). A disorder can also be found in multiple classifications (top-level disorders, you could say).
I created the models Disorder and Classification.
As we used SKOS:broader for the parents of a disorder, I created the links :broaders (= parents) and :narrowers (= children). There's also a :classifications link.
As nothing is too easy, I had to fork tripod to make it work in my environment which is Rails 4 (issue #14) and OpenRDF's Sesame (issue #15). I may have missed a part of code to patch.

Code
Here's (part of) my disorder model:

class Disorder
  include Tripod::Resource

  rdf_type RDF::SKOS.Concept # NB: this will change

  field # snip ...
  linked_to :broaders, RDF::SKOS.broader, class_name: 'Disorder', field_name: :broaders_uri, multivalued: true
  linked_from :narrowers, :broaders, class_name: 'Disorder', multivalued: true
  linked_to :classifications, RDF::SKOS.inScheme, class_name: 'Classification', multivalued: true
  # snip ...
end

And here is the Classification model:

class Classification
  include Tripod::Resource

  rdf_type RDF::SKOS.ConceptScheme

  field # snip...
  linked_from :narrowers, :broaders, class_name: 'Disorder', multivalued: true # a classification is also a top-level disorder
  linked_from :all_narrowers, :classifications, class_name: 'Disorder', multivalued: true
  #snip...
end

Now the problem
The broaders and narrowers of a disorder work great, thanks!
I can create a Classification instance so I'm sure that my model is loaded.
But as soon as I try to access the classifications of a disorder, I get this error:

undefined method `predicate' for nil:NilClass

The error occurs before I see any tripod log about loading the classifications data.
I'll comment as soon as I find my typo (still hoping it's one) or patched! Maybe classification[s] is a reserved keyword I didn't know.

Cheers,
Yannick

[fonji]

I was missing the latest commit, I merged just before Ric did it.
My bad. Sorry for your time.
My fork is updated with the correct code.
Everything is nice and beautiful in this world now.