:id_param option to load_resource allows specification of the param name to find members

lib/cancan/controller_resource.rb

@@ -121,11 +121,15 @@ module CanCan
     end
 
     def id_param
-      @params[parent? ? :"#{name}_id" : :id]
+      if @options[:id_param]
+        @params[@options[:id_param]]
+      else
+        @params[parent? ? :"#{name}_id" : :id]
+      end
     end
 
     def member_action?
-      new_actions.include?(@params[:action].to_sym) || @options[:singleton] || (@params[:id] && !collection_actions.include?(@params[:action].to_sym))
+      new_actions.include?(@params[:action].to_sym) || @options[:singleton] || ( (@params[:id] || @params[@options[:id_param]]) && !collection_actions.include?(@params[:action].to_sym))
     end
 
     # Returns the class used for this resource. This can be overriden by the :class option.

spec/cancan/controller_resource_spec.rb

@@ -327,7 +327,15 @@ describe CanCan::ControllerResource do
     lambda { resource.load_and_authorize_resource }.should raise_error(CanCan::AccessDenied)
     @controller.instance_variable_get(:@custom_project).should == project
   end
-
+  
+  it "should load resource using custom ID param" do
+    project = Project.create!
+    @params.merge!(:action => "show", :the_project => project.id)
+    resource = CanCan::ControllerResource.new(@controller, :id_param => :the_project)
+    resource.load_resource
+    @controller.instance_variable_get(:@project).should == project
+  end
+  
   it "should load resource using custom find_by attribute" do
     project = Project.create!(:name => "foo")
     @params.merge!(:action => "show", :id => "foo")