Polymorphic has_many :through Vs Inheritance

Rails
1

Hi everyone.
Ive part of a project that I need to refactor, and im having some
difficultly deciding which path to take. Perhaps someone can help, I
think its primarily a design question.

A Spec consists of many Nests and many Parts. Nests contain Parts.

Here’s what I have, which works well currently:

class Spec << ActiveRecord::Base
has_many :parts, :through => :speclines
has_many :nests, :through => :speclines
end

class Specline << ActiveRecord::Base
belongs_to :spec
belongs_to :part
belongs_to :nest
end

class Part << ActiveRecord::Base
has_many :specs, :through => :speclines
end

class Nest << ActiveRecord::Base
has_many :specs, :through => :speclines
end

Now the question is, how do I simplfy this?

Option 1 is polymorphic associations. But do they work with has_many
:through?

Or, seeing that nests and parts are similar, should I make them children
of a parent class that I then have the association on that? What would
that look like?

Any help would be appriciated.

-Dave