I am trying to implement REST APIs, so in my RoR3 application I have XML responses. Before to pass to a consumer the XML, I wuold like to check if there are errors and, if so, send back a response with error messages.

I read "Active Record Validations and Callbacks" guides on the RoR website, but it seems not work in my case.

I extract from the database a resource doing

@response = User.find_by_id(1)

and I wuold like, if possible, to add error to it.

Seeing some examples I have seen how to report errors in an XML file

format.xml  { render :xml => @response.errors }

but how I can add append new errors to the @response?

Maybe something like this:

errors.add(:password, "is invalid")