UIViewController is deallocated before delegate method is called - ios

Question

I have PreviewController : UIViewController which is used to show document in full screen it's part of UINavigationViewController.
Also it's delegate of UISplitViewController.
When it's pushed, it hides masterView of UISplitViewController. (Methods 1 - 3 - 2 are called)
When it disappears (by pressing "back" button), it shows masterView of UISplitViewController. (Methods 4 - 2 are called)
But there is a way to force closing PreviewController. In this case only method 4 is called and PreviewController is deallocated before UISplitViewController can send message and call Method 2.
How can I resolve this problem? Is there a way to force UISplitViewController to call it's delegate method? Or can I retain PreviewController in Method 4 and release it in Method 2 (using ARC)?
// Method 1
- (void)viewDidLoad
{
[super viewDidLoad];
self.hideMaster = YES;
UISplitViewController *splitViewController = [(AppDelegate *)[[UIApplication sharedApplication] delegate] splitViewController];
splitViewController.delegate = self;
}
// Method 2
- (BOOL)splitViewController:(UISplitViewController *)svc shouldHideViewController:(UIViewController *)vc inOrientation:(UIInterfaceOrientation)orientation
{
return self.hideMaster;
}
// Method 3
- (void)viewWillAppear:(BOOL)animated
{
self.hideMaster = YES;
UISplitViewController *splitViewController = [(AppDelegate *)[[UIApplication sharedApplication] delegate] splitViewController];
[splitViewController.view setNeedsLayout];
[splitViewController willRotateToInterfaceOrientation:self.interfaceOrientation duration:0];
}
// Method 4
- (void)viewWillDisappear:(BOOL)animated
{
self.hideMaster = NO;
UISplitViewController *splitViewController = [(AppDelegate *)[[UIApplication sharedApplication] delegate] splitViewController];
[splitViewController.view setNeedsLayout];
[splitViewController willRotateToInterfaceOrientation:self.interfaceOrientation duration:0];
}
// PreviewController is created in UIViewController which belongs to UINavigationController
PreviewController *previewVC = [[PreviewController alloc] initWithNibName:#"PreviewController" bundle:nil];
previewVC.documentURL = url;
[self.navigationController pushViewController:previewVC animated:YES]

Answer 1

You're currently not holding any strong reference to your PreviewController instance.
It should be enough to add a strong class property in your interface:
#property (nonatomic, strong) PreviewController *previewVC;
And then create the instance by using:
self.previewVC = [[PreviewController alloc] initWithNibName:#"PreviewController" bundle:nil];
This ensures the PreviewController will not be deallocated while your view controller is alive (unless you release it yourself).