Custom UIStoryboardSegue using segueWithIdentifier:source:destination:performHandler:

The point of segueWithIdentifier:source:destination:performHandler:

• Provide an alternative to UIViewController performSegueWithIdentifier:sender in cases where you also want to create a custom transition, without creating a segue subclass.
• Vend a segue that can be used as the return for segueForUnwindingToViewController:fromViewController:identifier

As noted above, this approach is only viable for segues which you would call manually -- i.e. not for segues that would otherwise be triggered via IB triggers.

So, for example, if you have a segue that needs to be triggered after a certain timeout period (such as a custom lock-screen), you could use segueWithIdentifier:source:destination:performHandler: to handle the custom transition.

-(void)appTimeoutLockScreen{    UIStoryboardSegue *segue =                 [UIStoryboardSegue segueWithIdentifier:@"LockScreenSegue"                                                 source:sourceVC                                            destination:destinationVC                                         performHandler:^{                     // transition code that would                      // normally go in the perform method                }];    // Dev is responsible for calling prepareForSegue and perform.    // Note, the order of calls for an IB triggered segue as well as    // a performSegueWithIdentifier segue is perform first, then    // prepareForSegue:sender. Manual segues need to inverse the call    // in order to ensure VC setup is finished before transition.    [self prepareForSegue:segue sender:self];    [segue perform];}

Another practical use for the method is unwinding segues. Using a similar scenarioto the previous example, we could use it to return a segue to transition from a lock screen back to the previous viewController:

-(UIStoryboardSegue *)segueForUnwindingToViewController:(UIViewController*)toVC                                      fromViewController:(UIViewController *)fmVC                                             identifier:(NSString *)identifier{    UIStoryboardSegue *segue =             [UIStoryboardSegue segueWithIdentifier:@"FromLockScreenSegue"                                             source:fmVC                                       destination:toVC                                     performHandler:^{                // transition code            }];    return segue;}