UITextField textFieldShouldBeginEditing called twice in iOS4

When you tap UITextField, you get two textFieldShouldBeginEditing calls. This looks like a bug in initial iOS4 release. Workaround is to use a BOOL flag to decide what you should do with that call:

- (BOOL)textFieldShouldBeginEditing:(UITextField *)textField
{
    if (self.allowEdit)
    {
        [self askUser];
        return NO;
    }
    return YES;
}

- (void)askUser
{
    if (self.alertVisible)
        return;    
    self.alertVisible = YES;
    
    UIAlertView *alert =
    [[UIAlertView alloc] initWithTitle:@"Please verify"
                               message:@"Do you want to edit?"
                              delegate:self
                     cancelButtonTitle:@"Cancel"
                     otherButtonTitles:@"Yes",
     nil];
    [alert show];
    [alert release];
}

- (void)alertView:(UIAlertView *)alertView
    clickedButtonAtIndex:(NSInteger)buttonIndex
{
    self.alertVisible = NO;
    if (buttonIndex == 1)
        [self doSomething];
}

The bug will (should) be fixed in some future iOS4 release, so it's more safe to isolate your work-around inside your own routines as much as possible to minimize possible unwanted side-effects.