Validating uniquesness through double association?

rubyonrails-talk
1

Hello all!

Could someone give me idea how to solve following problem.

In the model:

class A < ActiveRecord::Base   has_many :B end

class B < ActiveRecord::Base   belongs_to :A   has_and_belongs_to_many :C end

class C < ActiveRecord::Base   has_and_belongs_to_many :B end

Is it possible to validate that C has only B's that belong to the same A ? %)

Will be happy to see any answers))