Maintain a Link to Subviews in View Controller - objective-c

Question

Here's my situation: I have a UIViewController that manages a hierarchy of subviews, perhaps as shown below:
This view is built from a .xib. I would like to be able to maintain access to each subview of topView – that is, I want a pointer to each so that I can, for example, say something like:
[button1 setText:#"Hello!"];
Usually, to do this, I wire up each element to which I would like access using Interface Builder, resulting in a header that looks something like this:
#interface MyViewController : UIViewController
{
__weak IBOutlet UIView *view;
__weak IBOutlet UILabel *label;
__weak IBOutlet UIButton *button1;
__weak IBOutlet UIButton *button2;
}
#end
These instance variables are __weak, which is fine, since by the time my view controller "gets" them, they're already owned by my view controller's root view (which, confusingly, I labeled "topView" in my quick diagram). In fact, I want these references to be weak – when my root view is released, so too should all its subviews be released. Great.
But let's say I want to create a new element of the UI, maybe a custom button, entirely in code. I'll call this element CustomViewClass, which will be subclassed from UIView. The instance of CustomViewClass that I will create will be called customButton. As with the other subviews of my view, I would like "access" to customButton so that I can interact with it. I know, however, that like any other subview, customButton will be owned by its superview, and that's how it should be – again, I want it to be released whenever my view is released. This makes me think that I should declare this view as a __weak instance variable or property of my view controller. Let's do that:
#interface MyViewController : UIViewController
{
__weak IBOutlet UIView *view;
__weak IBOutlet UILabel *label;
__weak IBOutlet UIButton *button1;
__weak IBOutlet UIButton *button2;
__weak CustomViewClass *customButton;
}
#end
Then, in my implementation:
#implementation MyViewController
- (void)viewDidLoad
{
[super viewDidLoad];
customButton = [[CustomViewClass alloc] init];
[[self view] addSubview:customButton];
}
#end
As you've probably already realized, this won't work, and the compiler will throw a warning to boot. Something like:
Assigning retained object to weak variable; object
will be released after assignment
I currently dodge this sort of warning with some very poor style:
#implementation MyViewController
- (void)viewDidLoad
{
[super viewDidLoad];
CustomViewClass *customButtonLocal = [[CustomViewClass alloc] init];
[[self view] addSubview:customButtonLocal];
customButton = customButtonLocal;
}
#end
That way, I get what I want:
An instance of CustomViewClass on the screen...
...with exactly one owner, its superview...
...and no lingering variables (customButtonLocal is released immediately after the block ends).
But this can't be the "right" way to do this. So, finally, my question:
How should I be allocating and instantiating this programmatically-created __weak variable without using this middle-man workaround?

Answer 1

Make CustomViewClass *customButton a strong reference.
The reason why you usually declare variables for your subviews as __weak IBOutlet is that the existence of these links does not imply ownership. Subviews are owned by the object instantiated from a NIB/Storyboard. You own that object directly, and you also own its dependent objects indirectly.
The customButton is a different story: you create it programmatically, so your NIB/Storyboard does not own it. Therefore, you should make the reference to it __strong (which is the default when there are no ARC modifiers).