IPhone SDK Memory Management

Question

Hi,
I have following code:
(void) DismissWelcomeMessage: (UIAlertView *) view
[view dismissWithClickedButtonIndex:0 animated:YES];
(void) ShowWelcomeMessage
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Blah" message:@"Blah Blah" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
[alert show];
[self performSelector:@selector (DismissWelcomeMessage:) withObject: alert afterDelay: WELCOMEMESSAGEDELAY];
[alert release];
ShowWelcomeMessage is called first.
Why DissmissWelcomeMessage works fine and does not crash even though alert object is released?
Is it because Dismiss function uses copy of the object passed on stack as a parameter to function? But even then would not it be just a copy of the pointer pointed to the now deallocated object?
Or [alert release] just decriment reference counting and does not really do the same as delete in C++?

Answer 1

[[alert release]] just decrements the release count. dealloc is called on alert, like on any object, when its reference count raise 0.
The message [self performSelector:@selector (DismissWelcomeMessage:) withObject: alert afterDelay: WELCOMEMESSAGEDELAY]; queues an event which retains both self and alert. The Event Manager will release both after sending the message (after the delay).
The comments below traces the retain count of alert
(void) ShowWelcomeMessage {
UIAlertView *alert = [UIAlertView alloc] initWithTitle:@"Blah" message:@"Blah Blah" delegate:self
cancelButtonTitle:@"OK" otherButtonTitles:nil; // retain count = 1
alert show;
self performSelector:@selector (DismissWelcomeMessage:) withObject: alert
afterDelay: WELCOMEMESSAGEDELAY; // retain count = 2
alert release; // retain count = 1
An advice: don't use uppercase method name. Only Class names should be uppercased
(void) DismissWelcomeMessage: (UIAlertView *) view // should be "dismissWelcomeMessage"
(void) ShowWelcomeMessage // should be "showWelcomeMessage"