iPhone内存管理问题与对象生命周期

- (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: WELCOME_MESSAGE_DELAY]; 

    [alert release];
}

是因为Dismiss函数在函数执行时使用堆栈上传递的对象的副本作为参数吗?但即便如此,它难道不是指向现在已释放对象的指针的副本吗?