Strange crash : never access UI from background thread

*Edited : nothing wrong with the below code. In the XIB file, i dump in a UIWebView. Never set any delegate, never do anything with that UIWebView. It just crashes. Removing the UIWebView, everything works fine again. I use Automatic Reference Counting, and i think there's a bug with UIWebView.

My app crashes and here's the message :

Code:

bool _WebTryThreadLock(bool), 0x8213c10: Tried to obtain the web lock from a thread other than the main thread or the web thread. This may be a result of calling to UIKit from a secondary thread. Crashing now...

Here's what my code look like :

Code:

@implementation MyViewController 

- (void) viewDidLoad {
   [super viewDidLoad];
   [NSThread detachNewThreadSelector:@selector(doSmth) toTarget:self withObject:nil];
}

- (void) doSmth {
    // Do something here and don't update the UI
}

Here's the situations :
MyViewController is pushed into a navigation controller.
- When i go to MyViewController, stay there for a while until doSmth finishes. Then everything is fine.
- If i go to MyViewController, then quickly tap "Back", after a while (which i believe is when doSmth finishes), app crashes and it throws the message.


From what i understand, it should not be because of accessing UI from background thread, because :
- I'm sure i don't access UI in doSmth
- If it's the case, then app should crash for both situations.


So why it only crashes when i already tap "Back" button ?

 

I'm pretty sure it's not what you guys are saying.

I've created a new test project so that it isolates from my original project. In the new test project, i added only few lines of code as i already show in first post.

The behavior is consistent : if you drop a UIWebView into the XIB file, it crashes whenever you tap "Back" while the loading is still in progress. Throw away the UIWebView, it works again.

Here's how i go around this issue :

Code:

- (void) viewWillDisappear:(BOOL)animated {    
    // Is about to pop out
    if(self != self.navigationController.visibleViewController) {
        [_webview removeFromSuperview];
        _webview = nil;
    }
}

----------

I don't do much in doSmth. I even tried this but it's still crashes :

Code:

- (void) doSmth {
   @autorelease {
        // Do nothing
   }
}

 

No. I just dump the webview into the Xib file. That's it. I dont touch it at all.