iOS how to detect programmatically when top view controller is popped?

Question

Suppose I have a nav controller stack with 2 view controllers: VC2 is on top and VC1 is underneath. Is there code I can include in VC1 that will detect that VC2 has just be

Answer 1

One way you could approach this would be to declare a delegate protocol for VC2 something like this:

in VC1.h

@interface VC1 : UIViewController  {
...
}

in VC1.m

-(void)showVC2 {
    VC2 *vc2 = [[VC2 alloc] init];
    vc2.delegate = self;
    [self.navigationController pushViewController:vc2 animated:YES];
}

-(void)VC2DidPop {
    // Do whatever in response to VC2 being popped off the nav controller
}

in VC2.h

@protocol VC2Delegate 
-(void)VC2DidPop;
@end

@interface VC2 : UIViewController {

    id delegate;
}

@property (nonatomic, assign) id delegate;

...

@end

VC2.m

-(void)viewDidUnload {
    [super viewDidUnload];
    [self.delegate VC2DidPop];
}

There's a good article on the basics of protocols and delegates here.