问题
The problem is only happening with iOS4.3. I'm using ARC and my Base SDK is iOS6.
In -viewDidAppear of my view controller, I check if this is the first time the app has been started and if so, then I create and show a UIAlertView. I assign that UIAlertView to a strong property on the view controller and set self as the UIAlertView delegate.
self.uiAlertView = [[UIAlertView alloc] initWithTitle:@"Welcome!"
message:messageString
delegate:self
cancelButtonTitle:@"OK"
otherButtonTitles:@"View Tutorial Videos", @"Email Support", nil];
When I tap one of the buttons, the app crashes complaining that -alertView:didDismissWithButtonIndex: was sent to a deallocated instance. The delegate is the view controller that is displaying the UIAlertView.
On all subsequent launches of the app, when the UIAlertView isn't shown there are no problems. The view controller is definitely not being deallocated.
If I display the UIAlertView but set the delegate to nil, then there is no problem and the app continues working, so clearly the view controller hasn't been deallocated because I can keep using it.
What is happening? This only causes a problem with iOS4.3.
EDIT: Based on suggestions in the comments, I added some more log messages in different places.
I've discovered that the view controller IS getting dealloc'd, but only if that view controller displays the UIAlertView. What in the world would cause the view controller to get dealloc'd just because it sets itself as the delegate of a UIAlertView and then displays it?
My app delegate has a strong reference to the view controller, so there is absolutely no reason that I can see for the view controller to get dealloc'd.
EDIT 2: I've discovered that during start up my main view controller is being instantiated TWICE. The first one is the one creating the UIAlertView and that one is getting dealloc'd. The second one is the one that I've been able to interact with afterwards that made me think the view controller was still there and operable.
However, I can't figure out where or why my view controller would be created twice. I don't have any alloc/init statements for the view controller. It only exists in the MainWindow_iPhone.xib.
The first time viewDidLoad is called on my view controller, the stack frame above is [UIViewController view]. The second time viewDidLoad is called on the second instance of my view controller, the stack frame above is [UINib instantiateWithOwner:options:]
EDIT 3: I've "fixed" the problem, but I don't understand why this would happen. Perhaps you can help me understand.
In my MainWindow_iPhone.xib, I created my root view controller and assigned it to an IBOutlet on my app delegate. Instead, I deleted the view controller from the xib and created it in code in the -application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions ... and the problem disappeared.
Why in the world would the view controller be created twice when in the xib?
回答1:
I have this issue before. alertView:didDismissWithButtonIndex: is called after alertView: clickedButtonAtIndex:. You most likely deallocate the view controller in alertView:clickedButtonAtIndex by doing something like [self.navigationController popViewControllerAnimated:YES].
UIAlertView delegate is assign not weak reference. When delegate is deallocated, it is not set to nil automatically. That's reason why your code is crashed.
回答2:
i fixed this issue commenting this method (or deleting it).
- (void)actionSheet:(UIActionSheet *)actionSheet didDismissWithButtonIndex:(NSInteger)buttonIndex
{
NSLog(@"se apreto cancel");
}
as James Wang said, the didDismissWithButtonIndex is called after clickedButtonAtIndex so i commented it to avoid the crash.
来源：https://stackoverflow.com/questions/13146101/alertviewdiddismisswithbuttonindex-message-sent-to-deallocated-instance