module SimpleForm::MapType

def self.extended(base)
  base.class_attribute :mappings
  base.mappings = {}
end

def map_type(*types)
  map_to = types.extract_options![:to]
  raise ArgumentError, "You need to give :to as option to map_type" unless map_to
  self.mappings = mappings.merge types.each_with_object({}) { |t, m| m[t] = map_to }
end