How to create a pop-up when exiting a view? - ios

Question

So I'm making a photo editing app for school from last semesters project. When a user clicks the back button (in editor mode) which in my case is called "Product Selection" I'd like to have a pop-up come up and say "Do you want to delete everything and go back to product selection?" to see if they want to discard their work, and if the user selects yes, the entire project is discarded and they are put back in the lobby.
Where do I put this code to do this? I found the "Product Selection" button in the min story board but not sure what to do from there.
The code for the pop-up I was going to use is:
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"Notification"
message:#"Do you want to delete everything and go back to product selection?" delegate:self cancelButtonTitle:#"No" otherButtonTitles:#"Yes"];
[alert show];
[alert release]
Any help/wisdom would be extremely appreciated!

Answer 1

I would create a "Cancel" UIBarButton which executes a custom function:
- (void)cancelTapped {
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"Notification" message:#"Do you want to delete everything and go back to product selection?" delegate:self cancelButtonTitle:#"No" otherButtonTitles:#"Yes"];
[alert setTag:1];
[alert show];
}
And listens for the alert to return on:
- alertView:didDismissWithButtonIndex:
From there, I would write the logic to hide the page and pop the view.
- (void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex {
if (alertView.tag == 1 && buttonIndex == 1) {
// Delete data and return to lobby
[self.navigationController popViewControllerAnimated:YES];
}
}

Answer 2

Use this delegate method (don't forget adding UIAlertViewDelegate on your .h):
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"Notification" message:#"Do you want to delete everything and go back to product selection?" delegate:self cancelButtonTitle:#"No" otherButtonTitles:#"Yes"];
alert.cancelButtonIndex = 0;
[alert show];
-(void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex{
// If user confirmed:
if (buttonIndex != 0) {
// Do what you need.
}
}