ios - Completion handler for UINavigationController "pushViewController:animated"?

Question

I'm about creating an app using a UINavigationController to present the next view controllers. With iOS5 there′s a new method to presenting UIViewControllers:

presentViewController:animated:completion:

Now I ask me why isn′t there a completion handler for UINavigationController? There are just

pushViewController:animated:

Is it possible to create my own completion handler like the new presentViewController:animated:completion: ?

Answer 1

See par's answer for another and more up to date solution

UINavigationController animations are run with CoreAnimation, so it would make sense to encapsulate the code within CATransaction and thus set a completion block.

Swift:

For swift I suggest creating an extension as such

extension UINavigationController {

  public func pushViewController(viewController: UIViewController,
                                 animated: Bool,
                                 completion: @escaping (() -> Void)?) {
    CATransaction.begin()
    CATransaction.setCompletionBlock(completion)
    pushViewController(viewController, animated: animated)
    CATransaction.commit()
  }

}

Usage:

navigationController?.pushViewController(vc, animated: true) {
  // Animation done
}

Objective-C

Header:

#import <UIKit/UIKit.h>

@interface UINavigationController (CompletionHandler)

- (void)completionhandler_pushViewController:(UIViewController *)viewController
                                    animated:(BOOL)animated
                                  completion:(void (^)(void))completion;

@end

Implementation:

#import "UINavigationController+CompletionHandler.h"
#import <QuartzCore/QuartzCore.h>

@implementation UINavigationController (CompletionHandler)

- (void)completionhandler_pushViewController:(UIViewController *)viewController 
                                    animated:(BOOL)animated 
                                  completion:(void (^)(void))completion 
{
    [CATransaction begin];
    [CATransaction setCompletionBlock:completion];
    [self pushViewController:viewController animated:animated];
    [CATransaction commit];
}

@end