ios - UINavigationController does not release memory after back button is tapped -

i have mainviewcontroller , secondviewcontroller. secondviewcontroller pushed using segue (ios 7 app).
problem when button tapped , app mainviewcontroller, secondviewcontroller memory not released.

in prepareforsegue, don't allocation. merely set delegate secondviewcontroller (aka cvc below). collectionviewcontroller (aka secondviewcontroller) quite big user goes back-and-forth between main vc , secondviewcontroller memory usage keeps increasing , app crashes eventually.

-(void) prepareforsegue:(uistoryboardsegue *)segue sender:(id)sender { if ([segue.identifier isequaltostring:@"show gallery"]) {     collectionviewcontroller *cvc =  (collectionviewcontroller *)segue.destinationviewcontroller;     cvc.delegate = self; } } 

also, delegate weak reference:

@property (weak, nonatomic) id <collectioncellselecteddelegate> delegate; 

it's not enough information localize issue.

are sure collectionviewcontroller object leaking? mean it's possible issue caused non-released sub-object used in collectionviewcontroller code. can try profiler xcode instrument clarify it.

also issue may caused custom uistoryboardsegue subclass (of course if using it).

anyway, great take @ storyboard , collectionviewcontroller code