Question

I can’t make the static analyzer ‘like’ this code, but at the same time I cannot autorelease the object that gets stored into controller, so it is useless for the caller. With these 2 static methods I’ve tried to make it easier to display an activity controller over any view (without blocking tabs).

PZActivityOverlayController *view = [PZActivityOverlayController displayOverView:self.view];
// Later on, when complete
[PZActivityOverlayController remove:view];

Original code:

+ (PZActivityOverlayController *)displayOverView:(UIView *)aView {
  PZActivityOverlayController *controller = [[PZActivityOverlayController alloc] initWithFrame:aView.superview.bounds labelText:@"Loading"];
  [controller viewWillAppear:YES];
  [aView.superview insertSubview:controller.view aboveSubview:aView];
  return controller; // Potential leak of object stored into controller
}

+ (void)remove:(PZActivityOverlayController *)display {
  [display viewWillDisappear:YES];
  [display.view removeFromSuperview];
  [display release]; // However it won't leak because it gets released here
 }

Perhaps I have the chain of responsibility wrong here, but it’s only for convenience. The alternative would be writing what’s in the body of these methods everywhere (which violates DRY too much for me).

Answer 1

There’s a rule (say, convention) – nonautoreleased objects are returned by methods alloc&init…, new, retain, copy. All the rest methods are HAVE TO return autoreleased object.

In your case I’d rewrite the code above:

....
    return [controller autorelease];
}

+ (void)remove:(PZActivityOverlayController *)display {
    [display viewWillDisappear:YES];
    [display.view removeFromSuperview];
}

…

PZActivityOverlayController *view = [[PZActivityOverlayController displayOverView:self.view] retain];
// Later on, when complete
[PZActivityOverlayController remove:view];

[view release];