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POUnclear on how to properly remove a UIViewController from another UIViewController
 

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  1. POUnclear on how to properly remove a UIViewController from another UIViewController
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    <p>thank you for your time, (As a side note, this question pertains mostly to iOS 4.2.3, I am aware some of these issues could be resolved with moving the code base to iOS 5, however we would like to release this app for phones running iOS 4 as well.)</p> <p>I have a "MasterViewController" that is in charge of calling and dismising other UIVIewControllers.</p> <p>First we trigger a new one:</p> <p><em>In MasterViewController.m</em></p> <pre><code>-(IBAction)triggerPrime:(id)sender { [self clearHomeScreen]; NSUInteger randomNumber = arc4random() % 2; if (randomNumber == 0) { self.flashTextViewIsDisplayed = NO; ThinkOfViewController *thinkVC = [[ThinkOfViewController alloc] initWithNibName:@"ThinkOfViewController" bundle:nil]; self.thinkOfViewController = thinkVC; [thinkVC release]; self.picturePrimeViewIsDisplayed = YES; [self.view addSubview:self.thinkOfViewController.view]; } else if (randomNumber == 1) { self.picturePrimeViewIsDisplayed = NO; FlashTextPrimeViewController *flashVC = [[FlashTextPrimeViewController alloc] initWithNibName:@"FlashTextPrimeViewController" bundle:nil]; self.flashTextPrimeViewController = flashVC; [flashVC release]; self.flashTextViewIsDisplayed = YES; [self.view addSubview:self.flashTextPrimeViewController.view]; } </code></pre> <p>Let's say that our randomNumber is 0, and it adds the ThinkOfViewController to the subview, (This is a very basic screen, it essentially displays some text with some assets animating:</p> <p><em>In ThinkOfViewController.m</em></p> <pre><code>- (void)viewDidLoad { [super viewDidLoad]; self.thinkOf.alpha = 0.0; self.dot1.alpha = 0.0; self.dot2.alpha = 0.0; self.dot3.alpha = 0.0; self.background.alpha = 0.0; [self animateViews]; } -(void)animateViews { [UIView animateWithDuration:0.25 animations:^ { self.background.alpha = 1.0; }completion:^(BOOL finished) { [UIView animateWithDuration:0.75 delay:0.00 options:UIViewAnimationCurveEaseIn animations:^ { self.thinkOf.alpha = 1.0; }completion:^(BOOL finished) { [UIView animateWithDuration:0.20 delay:0.60 options:UIViewAnimationCurveEaseIn animations:^ { self.dot1.alpha = 1.0; }completion:^(BOOL finsihed) { [UIView animateWithDuration:0.20 delay:0.60 options:UIViewAnimationCurveEaseIn animations:^ { self.dot2.alpha = 1.0; }completion:^(BOOL finished) { [UIView animateWithDuration:0.20 delay:0.60 options:UIViewAnimationCurveEaseIn animations:^ { self.dot3.alpha = 1.0; }completion:^(BOOL finished) { [UIView animateWithDuration:0.50 delay:0.60 options:UIViewAnimationCurveEaseInOut animations:^{ self.view.alpha = 0.0; }completion:^(BOOL finished) { NSLog(@"all animations done"); [[NSNotificationCenter defaultCenter] postNotificationName:@"removeThinkOfView" object:nil]; }]; }]; }]; }]; }]; }]; } </code></pre> <p>As you can see, once the animation sequence is finished, I post a notification to NSNotificationCenter (which resides in the MasterViewController) to remove this viewController.</p> <p><em>In MasterViewController.m</em></p> <pre><code>-(void)removeThinkOfView { [self.thinkOfViewController.view removeFromSuperview]; [self showPicturePrime]; } -(void)showPicturePrime { if (self.picturePrimeViewController == nil) { PicturePrimeViewController *pVC = [[PicturePrimeViewController alloc] initWithNibName:@"PicturePrimeViewController" bundle:nil]; self.picturePrimeViewController = pVC; [pVC release]; [self.view addSubview:self.picturePrimeViewController.view]; } else { PicturePrimeViewController *pVC = [[PicturePrimeViewController alloc] initWithNibName:@"PicturePrimeViewController" bundle:nil]; self.picturePrimeViewController = pVC; [pVC release]; [self.view addSubview:self.picturePrimeViewController.view]; } } </code></pre> <p>Now a picturePrimeViewController is loaded and added to the subview, everything loads and displays fine. Now, to get a new prime, you simple swipe for a new one.</p> <p><em>In picturePrimeViewController.m</em></p> <pre><code>-(void)handleSwipeFromRight:(UISwipeGestureRecognizer *)gestureRecognizer { if (!transitioning) { [self performTransition]; } } -(void)performTransition { CATransition *transition = [CATransition animation]; transition.duration = 1.0; transition.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn]; transition.type = kCATransitionPush; transition.subtype = kCATransitionFromLeft; transitioning = YES; transition.delegate = self; [self.view.layer addAnimation:transition forKey:nil]; [UIView animateWithDuration:0.5 animations:^ { self.view.alpha = 0.0; }completion:^(BOOL finished) { NSLog(@"Transition Animation Complete"); }]; } -(void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag { transitioning = NO; [[NSNotificationCenter defaultCenter] postNotificationName:@"nextPrime" object:nil]; } </code></pre> <p>Now in the animationDidStop: Method, i again post another notification to the NSNotificationCenter back to the MasterViewController to signal another prime.</p> <p><em>In MasterViewController.m</em></p> <pre><code>-(void)nextPrime { if (self.picturePrimeViewIsDisplayed) { [self.picturePrimeViewController.view removeFromSuperview]; self.picturePrimeViewController = nil; [self showAPrime]; } if (self.flashTextViewIsDisplayed) { [self.flashTextPrimeViewController.view removeFromSuperview]; self.flashTextPrimeViewController = nil; [self showAPrime]; } } </code></pre> <p><strong>However!</strong> Upon swiping the right, the view animates properly but then I get a bad access crash when the ThinkOfViewController is attempting to dealloc it's UIViews. So for some reason, it is taking that the ThinkOfViewController a long time to dealloc, when I assumed when I called <code>[self.thinkOfViewController removeFromSuperview]</code>, it should of been removed immeditately. </p> <p>(Side note, the textFlashViewController has no problems, the only problems are comming with this ThinkOfViewController).</p> <p>Is this paradigm I set up a bad implmentation of dealing with UiViewController's comming in and out? I have read that delegation can help in this instance, I'm just not sure how that works. </p> <p>If any of you have any ideas, I would be so grateful, as I have mined through forums and documentations and cannot see a solution to my rather custom implmentation of dealing with these views.</p>
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    1. COMax, I did a project with many nested ViewControllers. I used the parent-child view relationships. My post here with the solution code added might help: http://stackoverflow.com/questions/9883820/multiple-viewcontrollers-containerview-childview-instance-of-viewcontroller -scott
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