View's holding strong references?

Question

Quick question: my ViewController has an IBOutlet for a UILabel would the ViewController's view automatically hold a strong reference to the label? And also, if I programmatically create a UIPopoverController ivar in ViewController and put the UIPopoverController ivar on the screen programmatically too would ViewController's view automatically hold a strong reference to that too?

Answer 1

You should keep a strong reference to any views that are not part of the view hierarchy. Your view controller already has a strong reference to its view property (the main view) and all subviews will be retained by their superview, so you don't actually need to hold a strong reference to them you can hold a weak reference to those views.

However, if you have any view which is not in the main view (for example an additional view defined in the .xib file that you might add to your main view at some point later, or one of the child views that you want to remove and re-add programatically) then you should hold a strong reference to these views.

Also note that when you hold a strong reference to a view in your view controller, you should set self.strongViewRef = nil in viewDidUnload because you don't need it when the view is unloaded (for example when the view controller is in the background eg. obscured by another full-screen view). The property will be automatically re-set to a new instance of that view when the view is loaded again.

Regarding the popover, it will be retained while it is presented (by the window I think) but I would recommend holding a strong reference to it while you need it and then setting that pointer to nil once you are done with it. This way you guarantee that you can access it when you need to, which in some cases may be just before it is presented or just after it is dismissed.

Answer 2

Apple suggests now to hold weak references to the views created through interface builder except for the root one - view hierarchy will take care of retaining the views

However if you create it manually you want to have at least local strong variable before you add freshly created view to the view hierarchy and then you can assign it to the weak ivar so it won't get lost immediately after assigning to the weak ivar, e.g.:

// Somewhere in .h
__weak UIView *_myView;

// Somewhere in .m
_myView = [[UIView alloc] init];
[self.view addSubview:_myView];

doesn't make much sense, _myView will be lost immediately

// Somewhere in .h
__weak UIView *_myView;

// Somewhere in .m
UIView *myLocalView = [[UIView alloc] init];
[self.view addSubview:myLocalView];
_myView = myLocalView;

is perfectly safe since you assigning a variable that is managed by the view hierarchy itself

UIPopoverController, on the other hand, according to the docs should be always retained by you (e.g. __strong ivar). More then that you will het a nasty error if you won't retain it.

Answer 3

You don't need to make an outlet strong as the viewcontroller is what should be held strongly and once it is gone there would be no reason to hold on to the outlet as the view is no longer there so having outlet weak is fine. The view holds strong pointer to them itself.

edit: sorry forgot to say yes you should keep strong pointer to the popovercontroller