Allow ControllerResource#resource_class to utilize Proc's.

lib/cancan/controller_resource.rb

@@ -146,6 +146,7 @@ def resource_class
       when false  then name.to_sym
       when nil    then namespaced_name.to_s.camelize.constantize
       when String then @options[:class].constantize
+      when Proc   then @options[:class].call(@controller)
       else @options[:class]
       end
     end

spec/cancan/controller_resource_spec.rb

@@ -239,6 +239,11 @@ class Section
     resource.send(:resource_class).should == Section
   end
 
+  it "should have the specified resource_class if Proc is passed to load_resource" do
+    resource = CanCan::ControllerResource.new(@controller, :class => Proc.new { |controller| CanCan::ControllerResource })
+    resource.send(:resource_class).should == resource.class
+  end
+
   it "should load parent resource through proper id parameter" do
     project = Project.create!
     @params.merge!(:controller => "categories", :action => "index", :project_id => project.id)