iOS EXC_BAD_ACCESS error in class - objective-c

Question

I'v encountered EXC_BAD_ACCESS error in my app. Or to be more specific in one of my classes. It is Custom UIAlertView class. I couldn't catch when it throws EXC_BAD_ACCESS in usage. Sometimes it works great just as expected, and in all suden it craches... Here is whole class
#implementation AlertPassword
int counter = 3;
#synthesize done;
#synthesize alertText;
#synthesize msg;
- (void) showAlert :(NSString*) title
{
if(counter != 3){
if(counter == 1)
{
NSString *msgs = #"Last warning";
msg = msgs;
}
else
{
NSString *msgs = [NSString stringWithFormat:#"WRONG PIN. %d times remaining",counter];
msg = msgs;
}
}
else
{
NSString *msgs = #"Enter your pin";
msg = msgs;
}
UIAlertView * alert = [[UIAlertView alloc] initWithTitle:#"Security" message:msg delegate:self cancelButtonTitle:#"Cancel" otherButtonTitles: nil];
_alert = alert;
_alert.alertViewStyle = UIAlertViewStyleSecureTextInput;
alertText = [_alert textFieldAtIndex:0];
alertText.keyboardType = UIKeyboardTypeNumberPad;
alertText.placeholder = #"Pin";
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(controlTextDidChange:)
name:UITextFieldTextDidChangeNotification object:alertText];
[_alert show];
[_alert release];
[[NSNotificationCenter defaultCenter] removeObserver:UITextFieldTextDidChangeNotification];
}
- (void)controlTextDidChange:(NSNotification *)notification {
{
NSString *pin = [[NSUserDefaults standardUserDefaults] stringForKey:#"Pin"];
if ([notification object] == alertText)
{
if (alertText.text.length == pin.length)
{
if(counter != 0)
{
if([alertText.text isEqualToString:pin])
{
[_alert dismissWithClickedButtonIndex:0 animated:NO];
[self.tableViewController openSettings];
counter = 3;
}
else
{
counter--;
[_alert dismissWithClickedButtonIndex:0 animated:NO];
[self showAlert:#""];
}
}
else
{
[_alert dismissWithClickedButtonIndex:0 animated:NO];
[[NSUserDefaults standardUserDefaults] setObject:NULL
forKey:#"Telephone"];
[[NSUserDefaults standardUserDefaults] setObject:NULL
forKey:#"Pin"];
[[NSUserDefaults standardUserDefaults] synchronize];
UIAlertView *av = [[UIAlertView alloc] initWithTitle:#"" message:AMLocalizedString(#"EraseData", nil) delegate:nil cancelButtonTitle:AMLocalizedString(#"Ok", nil) otherButtonTitles:nil];
counter = 3;
[av show];
[av release];
}
}
}
}
}
- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{
NSString *pincheck = [[NSUserDefaults standardUserDefaults] stringForKey:#"pinCheck"];
if (buttonIndex == 0)
{
if(pincheck.intValue == 1)
{
NSLog(#"app kill");
exit(0);
}
else
{
NSLog(#"dismiss");
}
}
}
#end
Here is where i initialize and use this class.
case 5:
NSLog(#"Add remove");
if (pincheck != NULL && pin != NULL){
if([pincheck isEqualToString:#"0"])
{
AlertPassword *alert = [AlertPassword alloc];
alert.tableViewController = self;
NSString *msg = #"Enter your pin code to access:";
[alert showAlert:msg];
// [alert release];
}
break;
}
else
{
NSLog(#"Is null");
[Menu load2View:self];
}
break;
I though maybe it was because i do not release alert. But adding [alert release]; Made to have EXC_BAD_ACCESS directly after the user tries to enter something. Without [alert release]; it works. But sometimes it craches with EXC_BAD_ACCESS
Also sometimes it gets
2012-11-08 12:11:27.451 kodinisRaktas[2485:19d03] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSMallocBlock__ dismissWithClickedButtonIndex:animated:]: unrecognized selector sent to instance 0x947aae0'
But I also have no idea why this happends
Please help, I'm pretty new to objective-c and ios, and I have no idea how to get rid of this, I guess someone with a bit of experience will see whats wrong in my code.
I'v just saw, that EXC_BAD_ACCESS or unrecognized selector throws if you push cancel for 4-5 times or more, and then try to type something.

Answer 1

EXC_BAD_ACCESS is mostly due to bad memory handling. The alert has most likely become an zombie... I would have the alert as a property with strong/retain. You should hold on to it while displaying. Not release after "show".
When you set up the first you can do like this
_alert = [[UIAlertView alloc] initWithTitle:#"Security" message:msg delegate:self cancelButtonTitle:#"Cancel" otherButtonTitles: nil]; // retain count: 1
Note calling "show" will also retain it, but that does not change the fact that you need to too.
[_alert show]; // retain count: 2
Wait for the delegate callback and release it.
- (void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex {
[_alert release], _alert = nil; // retain count in next run will be 0
}
Tip: It may be easier to handle if you use UIAlertView combined with blocks. http://gkoreman.com/blog/2011/02/15/uialertview-with-blocks/

Answer 2

I don't see where you initialize alert, anyway I suppose it's a class field, so retain it.If it's not a class instance variable, make it be so, this way you will always have a pointer to it.
[__NSMallocBlock__ dismissWithClickedButtonIndex:animated:]
You are sending this message to a raw malloc block, so probably alert has been released and points to a memory used for something else, something that's not an objc object.
Try to retain alert and see what happens.

Answer 3

May be you are passing wrong values to this "dismissWithClickedButtonIndex:animated:" method which is not recognizing the value signature please do a double check for that;

Answer 4

the excepted answer does make sense and is likely the cause
but what is this?
[NSNotificationCenter defaultCenter] removeObserver:UITextFieldTextDidChangeNotification];