ActiveRecord Polymorphic Inheritance

I am using RoR ActiveRecord polymorphic inheritance and was wondering
if it’s possible to access the base class’ association methods in the
invocation of either to_xml or to_json without having to depict the
base class data in the serialized string. Here are my classes:

base class

class Asset < ActiveRecord::Base
belongs_to :resource, :polymorphic => true
has_many :right_owners, :dependent => :destroy

derived class

class Song < ActiveRecord::Base
has_one :asset, :as => :resource, :dependent => :destroy

derived class

class Film < ActiveRecord::Base
has_one :asset, :as => :resource, :dependent => :destroy

If I instantiate the asset, as in the case of asset = Asset.find
(:first, :include=>:resource), I can easily call asset.to_xml

However sometimes, we absolutely need to have the concrete class and
not just the base class object or serialized state. If I instantiate
the song, how can I serialize the underlying asset’s right_owners data
without introducing the ‘asset’ as the base class navigational tie?
For example:

instantiate the song

song = Song.find(:first, :include=>:asset)

serialize XML or JSON that includes the underlying asset’s


I can do this but this but it is not compatible for our caller since

they don’t understand the nested base Asset #class
#or alternatively for json:

Is there a way to access and serialize the base class’ associative
methods, i.e. ‘right_owners’, without having to include the ‘asset’
information. That is ideally, I’m looking for

..... ..... .... ....

One workaround is to define the right_owners relationship on the Song
class but that feels redundant and doesn’t follow the DRY principle
especially considering there will be other types of derived classes
such as Films, etc…

If I define right_owners as a method on the Song class, it just
serializes the class name as an array rather treating it as a AR
association that I can further navigate. That is a custom method is
not being treated the same as the AR association method defined
with :has_one or :has_many.

Any insight is much appreciated. Thanks.

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