UIAlertView button results in a child NSThread - objective-c

Question

I would like a user to get a prompt screen, it would have yes and no options.
The problem is the UIAlertView cannot be called from child thread, if I call it from child thread I am getting a runtime error(EXC_BAD_ACCESS). I am using NSThread on IOS6.1
This is the code that i am using
-(void) construct
{
NSThread *initThread =[[NSThread alloc]initWithTarget:self selector:#selector(error) object:nil];
[initThread start];
}
- (void) error
{
//make sure it runs on the main thread
dispatch_async(dispatch_get_main_queue(), ^{
UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:#"Save"
message:#"Enter File Name"
delegate:self
cancelButtonTitle:#"Cancel"
otherButtonTitles:#"OK", nil];
alertView.alertViewStyle = UIAlertViewStylePlainTextInput;
[alertView show];
});
}
- (void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex
{
NSLog(#"Alert View dismissed with button at index %d",buttonIndex);
switch (alertView.alertViewStyle)
{
case UIAlertViewStylePlainTextInput:
{
UITextField *textField = [alertView textFieldAtIndex:0];
NSLog(#"Plain text input: %#",textField.text);
} break;
case UIAlertViewStyleSecureTextInput:
{
UITextField *textField = [alertView textFieldAtIndex:0];
NSLog(#"Secure text input: %#",textField.text);
} break;
case UIAlertViewStyleLoginAndPasswordInput:
{
UITextField *loginField = [alertView textFieldAtIndex:0];
NSLog(#"Login input: %#",loginField.text);
UITextField *passwordField = [alertView textFieldAtIndex:1];
NSLog(#"Password input: %#",passwordField.text);
}break;
default: break;
}
}
This is the error that I am getting:
[NSURLCacheInternal alertView:didDismissWithButtonIndex:]: unrecognized selector sent to instance 0x8653630
2013-07-26 16:12:35.738 iOSTrack[7455:c07] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSURLCacheInternal alertView:didDismissWithButtonIndex:]: unrecognized selector sent to instance 0x8653630'
*** First throw call stack:
(0x1e7a012 0x1796e7e 0x1f054bd 0x1e69bbc 0x1e6994e 0x7c0e13 0x408d66 0x408f04 0x20e7d8 0x266b014 0x265b7d5 0x1e20af5 0x1e1ff44 0x1e1fe1b 0x1dd47e3 0x1dd4668 0x3caffc 0x21cd 0x20f5)
libc++abi.dylib: terminate called throwing an exception

Answer 1

Most likely what is happening is that your UIAlertView is a local variable and it's getting destroyed before the delegate has a chance to run. You need to keep a reference to it around long enough such that your delegate has a chance to run and do it's work. Then you are in the clear. This concept applies to both ARC and manual memory managed based code.
See this related question: UIAlertViewDelegate class "self" instance gets dealloc'd before button gets pressed

Answer 2

The code I tried actually worked fine for me
The only difference is
[alertView show] => [alertView show]; you miss ;,a typo in question i guess
running the code in seperate thread
dispatch_queue_t myQueue = dispatch_queue_create("My Queue",NULL);
dispatch_async(myQueue, ^{
// Perform long running process
[self error];
});
- (void) error {
//make sure it runs on the main thread
dispatch_async(dispatch_get_main_queue(), ^{
UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:#"Save"
message:#"Enter File Name"
delegate:self
cancelButtonTitle:#"Cancel"
otherButtonTitles:#"OK", nil];
alertView.alertViewStyle = UIAlertViewStylePlainTextInput;
[alertView show];
});
}