Question

I have a UIView in my class (besides the original view) made in interface builder.

@interface TimeLineGrid : UIViewController {

UIView *toggleView;

}

@property (nonatomic, retain) IBOutlet UIView *toggleView;

I have synthesized it as well. I have implemented a swipe gesture so that when swiped up, the toggle view is added and when swiped down the toggle view is removed.

-(void)swipedUp {

    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDuration:2.0f];

    [UIView setAnimationTransition:UIViewAnimationTransitionFlipFromLeft forView:self.view cache:NO];

    [self.view addSubview:self.toggleView];

    [UIView commitAnimations];



}

-(void)swipedDown {

    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDuration:2.0f];

    [UIView setAnimationTransition:UIViewAnimationTransitionFlipFromRight forView:self.view cache:NO];

    [self.toggleView removeFromSuperview];

    [UIView commitAnimations];

}

It works fine when I swipe up once and when I swipe down after that. But when i swipe up once again, it crashes with EXC_BAD_ACCESS error. I know this has something to do with the retain count increasing when I addSubview and reducing when I removeSubview. Can someone shed more light on this? How do I achieve this toggle?

EDIT:
My view hierarchy is as follows:

->UIView (toggleView)
->UIView (mainView to which toggleView is being added)
 -->UIToolBar

Answer 1

Most likely, the view is being released when you call [self.toggleView removeFromSuperview];. I recommend that you restructure your code a little.

Since you are creating the view in IB, declare it in the header file as

IBOutlet UIView *toggleView;

Do not include the property call or the synthesize. Since you are not setting or getting the toggleView, just refer to it by the pointer.

In the implementation, set the pointer to nil in viewDidUnload and release it in dealloc. Then, adjust your toggle methods as follows:

-(void)swipedUp {
    if (![toggleView superview]) {

        [UIView beginAnimations:nil context:nil];
        [UIView setAnimationDuration:2.0f];

        [UIView setAnimationTransition:UIViewAnimationTransitionFlipFromLeft forView:self.view cache:NO];

        [self.view addSubview:toggleView];

        [UIView commitAnimations];
    }
}

-(void)swipedDown {

    if ([toggleView superview]) {

        [UIView beginAnimations:nil context:nil];
        [UIView setAnimationDuration:2.0f];

        [UIView setAnimationTransition:UIViewAnimationTransitionFlipFromRight forView:self.view cache:NO];

        [toggleView removeFromSuperview];

        [UIView commitAnimations];
    }
}

Here, the if clause will catch the event that the user swipes up twice in a row and not respond to the second swipe. Notice also that this uses toggleView in place of self.toggleView.

This should resolve the problem.