iphone UIAlertView Modal

Question

Is it possible to present a UIAlertView and not continue executing the rest of the code in that method until the user responds to the alert?

Thanks in advance.

Answer 1

An answer has already been accepted, but I'll note for anyone who comes across this question that, while you shouldn't use this for normal alert handling, in certain circumstances you may want to prevent the current execution path from continuing while an alert is being presented. To do so, you can spin in the run loop for the main thread.

I use this approach to handle fatal errors which I want to present to the user before crashing. In such a case, something catastrophic has happened, so I don't want to return from the method that caused the error which might allow other code to be executed with an invalid state and, for example, corrupt data.

Note that this won't prevent events from being processed or block other threads from running, but since we're presenting an alert which essentially takes over the interface, events should generally be limited to that alert.

// Present a message to the user and crash
-(void)crashNicely {

  // create an alert
  UIAlertView *alert = ...;

  // become the alert delegate
  alert.delegate = self;

  // display your alert first
  [alert show];

  // spin in the run loop forever, your alert delegate will still be invoked
  while(TRUE) [[NSRunLoop currentRunLoop] runUntilDate:[NSDate distantFuture]];

  // this line will never be reached
  NSLog(@"Don't run me, and don't return.");

}

// Alert view delegate
- (void)alertView:(UIAlertView *)alertView willDismissWithButtonIndex:(NSInteger)buttonIndex {
  abort(); // crash here
}