Scopes related question

Hello,
Have a question related scope definition. I need to define a scope
based on related model attribute values like this.

class Product < ActiveRecord::Base
belongs_to :currency

scope :with_currency, lambda { |currency|
unless currency.to_s.upcase == ‘ALL’

here I need to define a scope that would test for currency.char_code

to match a passed value

something like… This is where I need help

  where("currency.char_code = ?", currency.to_s.upcase)
end

}

end

class Currency < ActiveRecord::Base
attr_accessor : char_code
end

class LineItem < ActiveRecord::Base
belongs_to :product

scope :with_currency, lambda { |currency|
unless currency.to_s.upcase == ‘ALL’

here is another scope where I need help…

  where("product.currency.char_code = ?", currency.to_s.upcase)
end

}

end

Thanks for suggestions. Still learning the scoping magic.

figured out the answer to this problem. I needed to use :joins to
include associated models in scopes.