Rails - Jun 2006 - More idiomatic way of doing this

Folks,

I''m trying to write a validating filter that checks if the user  
exists and renders XML if not. Most of the controllers will be  
returning XML on some error or other so I''m including RenderError in  
ApplicationController.

Is my approach a sound one? Also, is there a shorter and more  
idiomatic way of writing this:

       if @user.nil?
         render_user_exists params[:username]
         false
       else
         true
       end

Rest of the code below...

lib/util/render_error.rb:

module RenderError

   def render_user_exists data
     render :partial => "shared/error",
        :system => "udb",
        :code => 201,
        :fatal => true,
        :message => "user exists",
        :property => "username",
        :baddata => data
   end

end

app/views/shared/_error.rxml:

xml.error system => @system, code => @code, fatal => @fatal do
   xml.message @message
   xml.property @property
   xml.baddata @baddata
end

app/controllers/application.rb:

require ''util/render_error''

class ApplicationController < ActionController::Base

   include RenderError

end

app/controllers/user_controller.rb:

class UserController < ApplicationController

   before_filter :verify_user

   private

     def verify_user
       @user = User.find_by_username params[:username]
       if @user.nil?
         render_user_exists params[:username]
         false
       else
         true
       end
     end

end

	Thanks, Joel

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