While trying to implement support for conditional GETting in a rest system, we have come across the fresh_when and stale? methods.

The following code works fine with 304 and not further rendering: if stale?(:etag => resource, :last_modified => resource.updated_at.utc) respond_to do |format| format.html # show.html.erb } end end

But accessing 1.xml will try to render the resource twice:

if stale?(:etag => resource, :last_modified => resource.updated_at.utc)
  respond_to do |format|
    format.html # show.html.erb
    format.xml  { 
      render :xml => @order.to_xml(:controller => self, :except => [:paid_at]) 
      }
  end
end

The error message:

ActionController::DoubleRenderError in OrdersController#show

Can only render or redirect once per action

RAILS_ROOT: /Users/guilherme/Documents/ruby/restfulie-test Application Trace | Framework Trace | Full Trace

/Library/Ruby/Gems/1.8/gems/actionpack-2.3.4/lib/action_controller/base.rb:900:in render_without_benchmark' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.4/lib/action_controller/benchmarking.rb:51:in render' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.4/lib/active_support/core_ext/benchmark.rb:17:in ms' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.4/lib/active_support/core_ext/benchmark.rb:10:in realtime' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.4/lib/active_support/core_ext/benchmark.rb:17:in ms' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.4/lib/action_controller/benchmarking.rb:51:in render' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.4/lib/action_controller/base.rb:1331:in send' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.4/lib/action_controller/base.rb:1331:in perform_action_without_filters' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.4/lib/action_controller/filters.rb:617:in call_filters' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.4/lib/action_controller/filters.rb:610:in perform_action_without_benchmark' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.4/lib/action_controller/benchmarking.rb:68:in perform_action_without_rescue' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.4/lib/active_support/core_ext/benchmark.rb:17:in ms' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.4/lib/active_support/core_ext/benchmark.rb:10:in realtime' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.4/lib/active_support/core_ext/benchmark.rb:17:in ms' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.4/lib/action_controller/benchmarking.rb:68:in perform_action_without_rescue' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.4/lib/action_controller/rescue.rb:160:in perform_action_without_flash' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.4/lib/action_controller/flash.rb:146:in perform_action' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.4/lib/action_controller/base.rb:532:in send' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.4/lib/action_controller/base.rb:532:in process_without_filters' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.4/lib/action_controller/filters.rb:606:in process' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.4/lib/action_controller/base.rb:391:in process' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.4/lib/action_controller/base.rb:386:in call' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.4/lib/action_controller/routing/route_set.rb:437:in `call'

Any suggestions?

Regards