Validate uniqueness on combined fields in DataMapper

Question

Hi. I want to be able to put entries in my database where the manufacturer will be represented multiple times but not the same combination of manufacturer and model. So "Sony(manufacturer), Tv(model)" is okay "Sony(manufacturer), OtherTv(model)" but the third entry "Sony(manufacturer), Tv(model)" is not okay since the combination of manufacturer and model is not unique. I tried with the :key => true validation but it doesn't seem to work. And I cannot do something like validates_uniqueness_of :manufacturer AND :model I guess. So how do you do it?

class Tvs
  include DataMapper::Resource

  property :id,           Serial
  property :manufacturer, String, :key => true
  property :model,        String, :key => true

  validates_uniqueness_of :
end

Answer 1

Nevermind. It seems this did the job:

class Tvs
  include DataMapper::Resource

  property :id,           Serial
  property :manufacturer, String, :unique_index => true
  property :model,        String, :unique_index => true

  validates_uniqueness_of :model, :scope => :manufacturer
end