Add support to unload and destroy a view.

[edchat]

This support will be added to the Load controller.
There will be a new event called "app-unload-view" to handle unloading and destroying a view. Calls to use the new "app-unload-view" would look like this:

params.view = view; 
this.app.emit("app-unload-view", params); 

I would also like to add some config options to make it easy to avoid having too many views loaded. Perhaps support for the app or a view to have these options:
"alwaysAutoUnload": which if set to true means the view will automatically be unloaded and destroyed after afterDeactivate is called for the view.

"autoUnloadCount": which is set to a number which is used to determine how many views (per constraint) to leave loaded when transitioning in the application.

"neverAutoUnload": which if set to true means this view will never be automatically unloaded and destroyed no matter how many views are loaded.

[edchat]

Christophe suggested that in addition to support for unloading a view with the emit of the "app-unload-view" event we should add a function which can be called to unload the view as well to make it easier for an app to unload views.

[nickcmaynard]

Agreed with Christophe's suggestion.

Back in the dojox/mobile world, I've often found myself dynamically creating and reaping hierarchical structures - ie. only when transferring up the hierarchical view tree, as opposed from any deactivation.

I'd need to control this kind of logic programmatically, so a function would be helpful.

[edchat]

I will add an unloadView function was added to main.js, it will take these parameters:
(/Object/view, /function?/callback)
So a call would look like:
app.unloadView(/Object/view, /function?/callback);

[cjolif]

shouldn't it be promised based instead of callback?

[edchat]

Yes, but I am going to have to convert all of the events that are using callbacks to be promise based, so I was thinking that I would do those all at the same time, if that is OK. I actually did not have any cases where the callback was needed, but thought it should be there just in case.

[cjolif]

that's indeed fine doing it later.

[edchat]

The basic view unload support is in, the event is "dapp-unload-view", but it is currently only called for app.unloadApp(). I still need to add the auto unload options listed above, and the app.unloadView(...) support.