Lazy Loading of Proxies

While working on a pureMVC project, I realised that there were N number of proxies registered with facade (yes, ApplicationFacade). The truth was, not all have been used during life cycle of a typical user functionality.

So what? It was merely difficult to categories the proxies for need of individual module/functionality.

The simple idea is to implement Lazy Loading / Lazy registration of proxy!

Instead of declaring statement at compile time like

facade.registerProxy(new MyProxy()); 

I overridden

retrieveProxy(...)

function in extended Facade class:

override public function retrieveProxy(proxyName:String):IProxy
{
 var proxyInstance:IProxy = super.retrieveProxy(proxyName);
 if(proxyInstance==null)
 {
 var myClass:Class = getDefinitionByName(proxyName) as Class;
 if(!myClass)
 return null;

 var proxyInstance:IProxy = new myClass();
 if(proxyInstance)
 registerProxy(proxyInstance);
 }
 return proxyInstance;
}

This also takes care of not registering duplicate proxy.
Uh oh! While doing this trick, I encountered on more problem.


ReferenceError: Error #1065: Variable myClass is not defined.

I banged my head and tried to figure out the reason. After digging for some time, I found that the (class) definition of proxy was somehow not been retrieved with

getDefinitionByName() 

.
It wasn’t possible to simply add import statements with those Proxy class names as Flex compiler ignores such unused (yes while compiling none of proxy was referenced) imports.

Simple trick worked:
in extended facade class constructer, I declared each proxy as variable, something like:

public class ApplicationFacade extends Facade
{
 public function ApplicationFacade(parameter:SingletonEnforcer)
 {
 super();

 var myProxy:MyProxy;
 }
}

and that’s all I wanted! The trick is this code doesn’t force an instance of proxy to be created, still at runtime when required, it finds definition of MyProxy class.

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