Serialization: (1) :methods with arguments and (2) scoped :include

Hello everybody

The to_xml and to_json serializers are pretty good for almost every purpose. However some extra feature would be nice to have in order to export a little more accurate data.

I tried to get a couple of improvements, keeping the old behaviors still working:

(1) With the :methods key we are able to include the result of instance methods assuming that are not accepting arguments or there are arguments with default value. The first improvement lets us to invoke a method with arguments, wrapping the method name and arguments into an array.

:methods => [:name]
:methods => [[:name, argument_1, argument_2, ...]]

(2) With the :include key we are able to include associated objects, however all instances are always associated. The second improvement lets us to scope the associated objects to include into the serialization.

:include => { :posts => { :records => @only_these_posts } }

I didn't try if a better approach would be scoping a subset of objects through named_scope, but in case of dynamic scope we should pass a lambda, so we still have to patch the serializer... isn't it?

To achieve these two behaviors, I changed just a couple of lines in rails/activerecord/lib/active_record/serialization.rb

Does it make sense? Or should I have a complete different approach?

Thanks.