Re: iOS 8: Can any of you guys think of why an async creation of a UIAlert would generate an exception on a show?
Re: iOS 8: Can any of you guys think of why an async creation of a UIAlert would generate an exception on a show?
- Subject: Re: iOS 8: Can any of you guys think of why an async creation of a UIAlert would generate an exception on a show?
- From: Alex Zavatone <email@hidden>
- Date: Wed, 29 Jul 2015 14:40:55 -0400
Huh. Within the @try block, we can see that the navigationControllerSupportedInterfaceOrientations: is being sent to the UIAlertController.
2015-07-29 14:15:56.967[719:244869] -[SignInViewController displayErrorMessage:] [Line 289] <- ***
2015-07-29 14:15:56.985 [719:244869] -[UIAlertController navigationControllerSupportedInterfaceOrientations:]: unrecognized selector sent to instance 0x156e29f0
0x156e29f0 is _alertController inside the instance of alert.
Yes, the view controller class this is happening in is conforming to UINavigationControllerDelegate and I have set the self.navigationController.delegate to self.
What I can't wrap my head around is why or how it is possible for something like this to happen.
On Jul 29, 2015, at 2:08 PM, Alex Zavatone wrote:
> I've got a completion block in an NSURLSessionDataTask that checks if the NSURLResponse statusCode is not 200 and in that case, it places a cell to a method to display a generic error message like so:
>
> // If no error occurs, check the HTTP status code.
> NSInteger HTTPStatusCode = [(NSHTTPURLResponse *)response statusCode];
>
> // If it's other than 200, then show it on the console.
> if (HTTPStatusCode != 200) {
> DLog(@"HTTP status code = %ld", (long)HTTPStatusCode);
> NSString *errorMessage = [NSHTTPURLResponse localizedStringForStatusCode:HTTPStatusCode];
> DLog(@"HTTP error message is: %@", errorMessage);
>
> // display error message;
> [self displayErrorMessage:errorMessage];
> return;
> }
>
>
> And in displayErrorMessage is will asks GDC to dispatch an async call to display the message on the main thread.
>
> // Error messages
> - (void)displayErrorMessage:(NSString *)errorMessage {
> DLog(@"<- ***");
> // handle on the main thread
> dispatch_async(dispatch_get_main_queue(), ^{
> NSString *internalErrorMessage = @"An error occurred. Please try again.";
>
> UIAlertView *alert = [[UIAlertView alloc]
> initWithTitle: nil
> message: internalErrorMessage
> delegate: nil
> cancelButtonTitle: @"OK"
> otherButtonTitles: nil, nil];
>
> if (alert) {
> [alert show];
> } else {
> DLog(@"For some reason, the alert instance isn't ready for a show.");
> }
> });
> }
>
> What's happening intermittently when I'm causing the server call to time out is that I'll get a bad access on the [alert show].
>
> I've spent all morning trying to narrow this down, to find out where the bad access is and why this is occurring. Sometimes in the stack trace, I'll see 3 or 4 calls to display the alert in different threads. Sometimes, I see that the [alert show] exception is being caused by navigationControllersupportedInderfaceOrientations: being sent to alert and the instruction pointer is on the [alert show line].
>
> I've included a screenshot of thread 1 to see if any of this makes any sense to anyone else.
>
> Thanks in advance if you're able to spend some time to help me out on this one.
>
> Adding an @try block around the [alert show] and retesting now.
>
> Stack trace screenshot below:
> http://i.imgur.com/KfILPLE.png
>
> - Alex Zavaotne
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