parameter_sanitization.rb

module ParameterSanitization

  # Convert blank strings to nil if type is Integer and nils are allowed
  #
  # @example
  #
  #   class User
  #
  #      include DataMapper::Resource
  #
  #      property :id, Serial
  #      property :some_fk_id, Integer
  #
  #      extend ParameterSanitization
  #
  #      treat_blank_as_nil :sales_group_id
  #
  #    end
  #
  def treat_blank_as_nil(*args)
    raise ArgumentError unless args.all? { |arg| properties[arg.to_sym] }
    args.map { |arg| arg.to_sym }.each do |p|
      if properties[p].type == Integer && properties[p].allow_nil?
        define_method "#{p}=" do |value|
          attribute_set(p, value == '' ? nil : value)
        end
      end
    end
  end

end