A user asked me when they should create a sub-controller for a nested component instead of putting it all in the main controller. There is no hard and fast rule only two guidelines. 1) It is nice to use a sub-controller to modularize your code and place it along with the component in its own directory. 2) If your events do not need access to anything outside the component they are thrown from (other than the model) then use a controller for that component (the context passed to your event handlers will be that component). If you were to place them in the main controller not only would it clutter it up but since the handler context will now be the main component you will have to use dot notation to dig down into the component you need to deal with- sometimes necessary but never desirable.