Question

I persist to be a little confused about when to put something in a viewController and when to put it inside an AppDelegate, and if it is ok to reference viewController methods from the AppDelegate (i know you can but that doesn’t mean it is encouraged).

Really, I wouldn’t be confused if it weren’t for all this multi-tasking stuff that seems to complicate the concepts for me. First, if anyone knows of a good, thorough and easy to read overview of how to deal with multitasking, I’d love to know.

Here’s the deal: there are things I need my app to do when it loads, whether loading fresh or loading from the background. Stuff like perform a network reachability test, setup the interface based on data received from the internet, and this or that.

One of my main questions relates to how the viewcontroller’s view interacts with background states. If the app resumes from the background and the view is immediately present without loading, then I assume it is still in memory and I have verified that viewDidLoad was not called with a basic NSLog. So, is it safe to say that any and all objects retained by my viewcontroller (like the data models and all subviews) are thus still in memory? If not, what’s the best practice discovering which objects need to be re-loaded, what are still there, etc?

Answer 1

I think it’s safe to assume that the standard memory management rules apply, even in a multi-tasking environment. That means that your controller, and anything you’ve got a reference to in your controller should still be valid until either:

1. You explicitly deallocate your controller/objects
2. Your app terminates

It seems like your assumption is that the system is going to mess with your objects behind your back, which (I hope) can’t happen. Those methods are there in the app delegate in case you want to explicitly do anything when those particular events occur.

Regarding the viewDidLoad question, you could implement viewDidUnload or check the isViewLoaded method to make sure your view wasn’t unloaded due to a low memory condition or otherwise. More on this in the UIViewController documentation.