Tuning The Legs
The Robotlegs MVCS implementation was designed to be convenient: quick-n-easy for common use cases. Nothing is free, of course, and that convenience comes at a cost. I want to highlight a few things that can be tweaked to improve performance for applications that really need it.
Automatic Mediation
In order to determine the scope of a view component, Robotlegs listens to the contextView for bubbling capture-phase ADDED_TO_STAGE events:
MediatorMap.as#L233
MediatorMap.as#L260
Every display object that lands on the stage inside the contextView is checked against a mapping dictionary. This can be quite expensive for complex display object hierarchies where there is a lot of re-parenting. It’s also the only option available if you want to keep your view components completely framework-unaware. If, however, you’re prepared to modify your components slightly (it’s a one-liner) then you can try out this utility:
http://github.com/eidiot/robotlegs-utilities-LazyMediator
Instead of listening for ADDED_TO_STAGE events emitted by every component, we listen only for custom events dispatched by view components that explicitly require mediation.
Note: This utility currently only supports the MediatorMap and needs to be expanded to support the ViewMap. Fork and improve!
Default Injection Points
The actors in the MVCS package have a number of pre-configured injection points (dependencies). When you extend mvcs.Command all you are really doing is inheriting some dependencies:
Whilst handy, it is quite seldom that we actually use all of those in a given Command.
A much cleaner, and ever-so-slightly cheaper approach is to declare only the dependencies that you actually need. Instead of extending Actor or Command (this doesn’t work so well for the Mediator class), just create a vanilla class and declare your dependencies manually:
public class MyCommand
{
[Inject]
public var injector:IInjector;
public function execute():void
{
injector.mapClass( Vehicle, Car );
}
}
Remember, the Robotlegs apparatus is already mapped for you if you need anything:
Notice that the IEventMap is not mapped as a value or singleton – you’ll get a new IEventMap instance whenever you ask for one.
That’s it for now!
