App crashes when hitting rewind button multiples times - iphone

Question

Application crashes and message is program received signal "EXC_BAD_ACCESS" when hitting purposely on rewind button multiple times just to test application on iPhone device.
-(void)rewind:(id)sender{
[timer invalidate];
audioPlayer.currentTime = 0;
MainViewController *viewController = [[MainViewController alloc] init];
viewController.view.frame = CGRectMake(0, 0, 320, 480);
[self.view addSubview:viewController.view];
[self.view addSubview:toolbar];
[viewController release];
[self playpauseAction:_playButton];
}
-(void)playpauseAction:(id)sender {
if([audioPlayer isPlaying])
{
[sender setImage:[UIImage imageNamed:#"Play Icon.png"] forState:UIControlStateSelected];
[audioPlayer pause];
[self pauseTimer];
[self pauseLayer:self.view.layer];
}else{
[sender setImage:[UIImage imageNamed:#"pause.png"] forState:UIControlStateNormal];
[audioPlayer play];
[self resumeTimer];
[self resumeLayer:self.view.layer];
if(isFirstTime == YES)
{
self.timer = [NSTimer scheduledTimerWithTimeInterval:11.0
target:self
selector:#selector(displayviewsAction:)
userInfo:nil
repeats:NO];
isFirstTime = NO;
}
}
}
-(void)pauseTimer{
pauseStart = [[NSDate dateWithTimeIntervalSinceNow:0] retain];
previousFireDate = [[timer fireDate] retain];
[timer setFireDate:[NSDate distantFuture]];
}
-(void)resumeTimer{
float pauseTime = -1*[pauseStart timeIntervalSinceNow];
[timer setFireDate:[previousFireDate initWithTimeInterval:pauseTime sinceDate:previousFireDate]];
}
-(void)resumeLayer:(CALayer*)layer
{
CFTimeInterval pausedTime = [layer timeOffset];
layer.speed = 1.0;
layer.timeOffset = 0.0;
layer.beginTime = 0.0;
CFTimeInterval timeSincePause = [layer convertTime:CACurrentMediaTime() fromLayer:nil] - pausedTime;
layer.beginTime = timeSincePause;
}
-(void)pauseLayer:(CALayer*)layer
{
CFTimeInterval pausedTime = [layer convertTime:CACurrentMediaTime() fromLayer:nil];
layer.speed = 0.0;
layer.timeOffset = pausedTime;
}
i don't know why it is crashing may be because of the resume timer or may be because of the view controller i released.

Answer 1

Why do you alloc and init your MainViewController inside of your rewind function? that seems odd to me, normally you only need to initialize your viewcontroller once, not every time a method is called. And similarly, you release it at the end of the method, which is also strange. Generally errors that take multiple clicks to be caused are caused by memory management problems. I'm guessing that something is being removed from memory (possibly your view controller) and then you are trying to access it, giving you a bad access error.
To debug this, use NSZombies, which allows you to see what was removed from memory. A tutorial of how to use it can be found here