rails validate uniqueness within inheritance

Question

I have to models: Tag and TagNumeric each one with a category field

I shouldn't be able to create Tags of different types with the same category. How can I validate this?

EDIT:

I forgot to mention

TagNumeric < Tag

class Tag
 include Mongoid::Document

 validates_presence_of :type, :value

 field :category, type: String
 field :value, type: String
 field :color, type: String
 validates :value, :presence => true, :uniqueness => {:scope => :category}



class TagNumeric < Tag

  field :value, type: Integer

it 'its category should be unique within the Tag class type' do
  Tag.create(category: 'Movie', value: 'Avatar')
  TagNumeric.create(category: 'Movie', value: 'Iron man').should_not be_valid
end

Answer 1

If anybody is having the same problem here is how I solved it

validate :uniqueness_within_category
def uniqueness_within_category
  first_category_type = (Tag.find_by(category: self.category).nil?)? 'none' : Tag.find_by(category: self.category)._type
  if first_category_type == 'none'
    #It doesnt exist then should be allowed
    return
  end
  #If it exists within another class type then shouldnt be allowed
  if self._type != first_category_type
    errors.add(:category, 'Must be unique within tag type')
  end
end

Testing started at 6:22 PM ...

1 examples, 0 failures, 1 passed