module ShopifyAPI::Metafields

def add_metafield(metafield)
  raise ArgumentError, "You can only add metafields to resource that has been saved" if new?
  metafield.prefix_options = {
    :resource => self.class.collection_name,
    :resource_id => id
  }
  metafield.save
  metafield
end

def metafields
  Metafield.find(:all, :params => {:resource => self.class.collection_name, :resource_id => id})
end