Chained Polymorphic Association and the missing type field

I have a chained polymorphic relationship. I will try to describe it
as best as I can.

Imagine:

    Group             (polymorphic)
            \
             |
           Tag          (polymorphic)
               \
               |
              Article

The idea being I can TAG many ARTICLES. I can also GROUP many TAGS.
And enjoy using both TAG and GROUP in more creative ways. I also use
proxy classes (GROUPABILITY and TAGABILITY) to encapsulate the
relationships. Both Groupability and Tagability are where
the :polymorphic => true statement resides. Then I use has_many with
a :through statement to do most of the relational work.

    Group
            \
             > Groupability   (real polymorphic)
             |
           Tag
               \
               > Tagability   (real polymorphic)
               |
              Article

After creating this relationship, the Tagabilty works just fine. The
Tagable_id and Tagable_type field are populated correctly. The
Groupability appears to work fine HOWEVER while the groupable_id field
is populated correctly , the groupable_type field remains nil. I
(believe) I have checked all my syntax which looks correct.

Are there any known bugs with this type of chained polymorphism or
some trick I am missing? Is the belongs_to on the polymorphic =
true line, simply appended with “_type” to determine the proper field
in the database to set the value? Is there a manual way of setting the
_type field for the proper class? How can I debug this when I am
getting no errors?

Steve Woolley
[email protected]

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