在alertview显示时，请勿连接segue

Question

I got a push segue connected in storyboards and then I'm using the prepareForSegue method like this:

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([[segue identifier] isEqualToString:@"start"] && self.name.textField.text == nil)
    {


        UIAlertView *message = [[UIAlertView alloc] initWithTitle:@"Test"
                                                          message:@"Test
                                                         delegate:self
                                                cancelButtonTitle:@"OK"
                                                otherButtonTitles:nil];
        [message show];

    }
}

What I want to do is that if the "if" is true, there pops an alert box and preforms the segue, but I just want to show the alert box, and I don't want to preform the segue. How can I solve this?

Answer 1

prepareForSegue:sender: is called when the segue is about to be performed. You cannot cancel it at that point.

The method you should be overriding if you want to be able to cancel a segue is shouldPerformSegueWithIdentifier:sender: .

Answer 2

I think you need to reevaluate your logic here and remove the conditional from prepareForSegue

Using UIAlertDelegate

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {
    NSString *title = [alertView buttonTitleAtIndex:buttonIndex];
    if([title isEqualToString:@"OK"]) {
      [self performSegueWithIdentifier:@"My Segue" sender:self];
      return;
    } // else do not perform segue
}

Answer 3

I dont think you can stop from at this point.

But you can use - (BOOL)shouldPerformSegueWithIdentifier:(NSString *)identifier sender:(id)sender from iOS 6.

Answer 4

Try giving your segue a different name and only call that segue (eg " [self performSegueWithIdentifier: @"MyRealStartSegue" sender: sender] ") if the alert is not displaying.

Of course this means you need to check these conditions outside of the " prepareForSegue " method. Perhaps an IBAction when some button is pressed?