module MoneyAccessor::ClassMethods

def money_accessor(*columns)
  variable_get = self <= Struct ? :[]  : :instance_variable_get
  variable_set = self <= Struct ? :[]= : :instance_variable_set
  Array(columns).flatten.each do |name|
    variable_name = self <= Struct ? name : "@#{name}"
    define_method(name) do
      value = public_send(variable_get, variable_name)
      value.blank? ? nil : Money.new(value)
    end
    define_method("#{name}=") do |value|
      if value.blank? || !value.respond_to?(:to_money)
        public_send(variable_set, variable_name, nil)
        nil
      else
        money = value.to_money
        public_send(variable_set, variable_name, money.value)
        money
      end
    end
  end
end