UIAlert 怎樣多個實例化對象使用同一個delegate

Alert views are pop-up views that appear over the current view on the iPhone.

Creating and showing an alert:

    UIAlertView *alert = [[[UIAlertView alloc] initWithTitle:@"Really reset?" message:@"Do you really want to reset this game?" delegate:self cancelButtonTitle:@"Cancel" otherButtonTitles:nil] autorelease];
    // optional - add more buttons:
    [alert addButtonWithTitle:@"Yes"];
    [alert show];

If you add the UIAlertViewDelegate protocol to your controller, you can also add the following method which is called after the user dismisses the alert view:

- (void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex {
    if (buttonIndex == 1) {
        // do stuff
    }
}

Button indices start at 0 (for the cancelButton specified in the alloc/init), and go up by 1 for each addButtonWithTitle call you add. If you have a lot of alerts, your didDismiss method can keep track of which one is being dismissed if you add the setTag call to the alert initialization: [alert setTag:23];

    UIAlertView *alert = [[[UIAlertView alloc] initWithTitle:@"Error" message:@"I'm sorry Dave, I'm afraid I can't do that." delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil] autorelease];
    [alert setTag:12];
    [alert show];

... later ...

- (void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex {
    if ([alertView tag] == 12) {    // it's the Error alert
        if (buttonIndex == 0) {     // and they clicked OK.
            // do stuff
        }
    }
}