PureMVC

QUESTION:

Answer:

 This is the cannonical deferred instantiation problem. 

The simplest starup scenario for a Flex or AIR app is that the MXML application creates itself first (the view components), then the PureMVC appraratus we build attaches itself to the MXML app by registering Mediators that have references to the already constructed view components in its hierarchy.

 

However a feature of Flex is deferred instantiation of view components. In a ViewStack, for instance, although several children may be defined in the MXML, only the first visible child will be instantiated by default (creationPolicy="auto"). The other children will be instantiated only when you navigate to them. This is nice because it helps startup go faster, and the user may not navigate to all the children, so time and memory is conserved.

 

Unfortunately, now our simple scenario above is no longer enough, because at startup time, we don't have references to all the view components that will eventually need mediation. Although we could register the mediators and later give them references to the view components as they are created, that sort of defeats the point of deferred instantiation. So we need to defer the creation and registration of the Mediator as well.

 

Inevitably, you will have an app complex enough that you have to deal with this problem. Then you need to study the release notes and source code for the Slacker demo.