Why to_xml on ActiveResource does not work well?

Question

I have several ActiveResource model in my project. There was so strange to me when I called to_xml on my ActiveResource. The options that I passed to to_xml like :only and :except doesn't work at all. On ActiveRecord, it works really well. Anyone knows?

class Node < ActiveResource::Base
   self.site = NODE_SERVER
end

# node has uuid, name, type attributes
node = Node.find("3333")
node.to_xml(:only => [:uuid])

# after here, i still get all attributes

Answer 1

You say "after here, I still get all attributes". It looks like you think node.to_xml will change the node itself, but that's not the case. You have to do

xml = node.to_xml(:only => [:uuid])

and then refer to xml.

Answer 2

The implementation of ActiveResource::Base#to_xml is different than ActiveRecord::Base.

See http://api.rubyonrails.org/classes/ActiveResource/Base.html#M000914

ActiveResource::Base#to_xml only accepts :indent, :dasherize, :camelize and :skip_instruct.

Answer 3

The to_xml methods on ActiveRecord and ActiveResource are independent implementations. That means that you cannot expect them to behave exactly the same or take the same arguments.