iOS: How to run a function after Device has Rotated (Swift)

The viewWillTransitionToSize delegate method gets called with a UIViewControllerTransitionCoordinator conforming object. A method that protocol declares is animateAlongsideTransition(_:animation, completion:). You can use that to have code execute after the transition is complete.

override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {    super.viewWillTransition(to: size, with: coordinator)    coordinator.animate(alongsideTransition: nil) { _ in        // Your code here    }}

Above answer https://stackoverflow.com/a/26944087/6583492 is absolutely right, thanks to Acey and Moonwalkr. But for swift 3.0 it will looks like the following

override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {    super.viewWillTransition(to: size, with: coordinator)    coordinator.animate(alongsideTransition: nil) { _ in        // Your code here    }}

Although not asked for here Objective C version:

- (void)viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator {[coordinator animateAlongsideTransition:^(id<UIViewControllerTransitionCoordinatorContext>  _Nonnull context) {    // change any properties on your views} completion:^(id<UIViewControllerTransitionCoordinatorContext>  _Nonnull context) {    UIDeviceOrientation orientation = [UIDevice currentDevice].orientation;    if( UIDeviceOrientationIsPortrait(orientation) ) {        NSLog(@"portrait");    } else {        NSLog(@"landscape");    }  }];}