heartcombo--simple_form/lib/simple_form/map_type.rb

require 'active_support/core_ext/class/attribute'

module SimpleForm
  module 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
  end
end