ViewController.m

- (void)viewDidDisappear:(BOOL)animated {
    [super viewDidDisappear:animated];
    
    [self.capture stop];
    [self.capture.layer removeFromSuperlayer];
    self.capture = nil;
}

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];

    self.capture = [[ZXCapture alloc] init];
    self.capture.delegate = self;
    self.capture.rotation = 90.0f;
    self.capture.layer.frame = self.view.bounds;
    [self.view.layer addSublayer:self.capture.layer];
    [self.view bringSubviewToFront:self.decodedLabel];
    [self.view bringSubviewToFront:self.scanImageView];
}