Replace a UIViewController in the UINavigationController hierarchy

Question

I have an iPhone app which uses a standard implementation of UINavigationController for the app navigation.

I am trying to figure out a way to replace a view controller in the hierarchy. In other words, my app loads into a rootViewController and when the user presses a button, the app pushes to firstViewController. Then the user pushes another button to navigate the app to secondViewController. Again the use navigates down to another view controller, thirdViewController. However, I want the BackButton of the thirdViewController to pop back to firstViewController.

Essentially, when the user pushes to thirdViewController, I would like it to replace secondViewController in the navigation hierarchy.

Is this possible? I know it is using Three20, but I'm not in this case. Nevertheless, if it's possible in Three20, then it certainly should be using straight SDK calls. Does anyone have any thoughts?

Cheers, Brett

I would also look into Unwind Segues, they're useful for accomplishing this kind of thing. Awesome SO answer on them here: http://stackoverflow.com/questions/12561735/what-are-unwind-segues-for-and-how-do-you-use-them — jrisberg, Jul 07 '15 at 20:26
In the given example, wouldn't you simply pop (that will get rid of the second one), and then push (you now have 1-3). Alternately, if it's a "different button", when you're on 1-2-3, simply pop twice and you'll be on 1. — Fattie, Jan 05 '18 at 00:11

score 58 · Accepted Answer · edited Nov 26 '17 at 18:33

58

Pretty Simple, when about to push the thirdViewController instead of doing a simple pushViewController do this:

NSArray * viewControllers = [self.navigationController viewControllers];
NSArray * newViewControllers = [NSArray arrayWithObjects:[viewControllers objectAtIndex:0], [viewControllers objectAtIndex:1], thirdController,nil];
[self.navigationController setViewControllers:newViewControllers];

where [viewControllers objectAtIndex:0] and [viewControllers objectAtIndex:1] are your rootViewController and your FirstViewController.

edited Nov 26 '17 at 18:33

Shaheen Ghiassy

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answered Dec 24 '11 at 21:57

Ecarrion

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after this code, do I still need to call `pushViewController`? – Rod Aug 31 '18 at 16:19

score 23 · Answer 2 · edited Jul 07 '15 at 20:22

23

NSMutableArray *viewController = [NSMutableArray arrayWithArray:[navController viewControllers]];
[viewController replaceObjectAtIndex:1 withObject:replacementController];
[navController setViewControllers:viewController];

See the UINavigationController class reference for more information.

edited Jul 07 '15 at 20:22

Necreaux

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answered Dec 24 '11 at 21:55

JustSid

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Thanks, mate. This solution handled it. Cheers. – Felipe May 03 '16 at 13:39

score 18 · Answer 3 · answered Dec 10 '16 at 05:07

18

A cleaner way in Swift should be:

extension UINavigationController {
  func replaceTopViewController(with viewController: UIViewController, animated: Bool) {
    var vcs = viewControllers
    vcs[vcs.count - 1] = viewController
    setViewControllers(vcs, animated: animated)
  }
}

answered Dec 10 '16 at 05:07

duan

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Clean and pretty +1 – Nik Kov Oct 04 '18 at 13:15

score 4 · Answer 4 · edited Jun 09 '13 at 17:15

It is not possible to animate the transition if you simply replace the viewController in the navigation controllers view controller array. I would recommend doing the following in the viewWillAppear method of the 3rd view controller.

-(void) viewWillAppear:(BOOL)animated
{
   NSArray *vCs=[[self navigationController] viewControllers];
   NSMutableArray *nvCs=nil;
   //remove the view controller before the current view controller
   nvCs=[[NSMutableArray alloc]initWithArray:vCs];
   [nvCs removeObjectAtIndex:([nvCs count]-2)];
   [[self navigationController] setViewControllers:nvCs];
   [super viewWillAppear:animated];
}

Skoua · Answer 5 · 2018-08-21T15:10:43.623

3

Swift 4 version:

if var viewControllers = navigationController?.viewControllers {
    viewControllers[viewControllers.count - 1] = newViewController
    navigationController?.viewControllers = viewControllers
}

edited Aug 21 '18 at 15:10

answered Sep 06 '16 at 09:28

Skoua

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score 2 · Answer 6 · answered Feb 11 '14 at 22:47

Since you are just trying to pop twice from the ViewControllers stack, you can probably get the same result by calling

- (NSArray *)popToViewController:(UIViewController *)viewController animated:(BOOL)animated

from the back button of the thirdViewController

score 2 · Answer 7 · edited Jan 23 '16 at 16:34

- (void)swapTopViewController:(UIViewController *)topViewController{
    NSArray *viewControllers = [self.navigationController viewControllers];
    NSMutableArray *editableViewControllers = [NSMutableArray arrayWithArray:viewControllers];
    [editableViewControllers removeLastObject];
    [editableViewControllers addObject:topViewController];
    [self.navigationController setViewControllers:editableViewControllers];
}

score 1 · Answer 8 · answered Dec 16 '17 at 05:59

1

extension UINavigationController {

    func setTop(viewController: UIViewController) {
        viewControllers = [viewController]
    }

}

answered Dec 16 '17 at 05:59

Elijah

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wouldn't that remove all of them, and leave only the one?? – Fattie Jan 04 '18 at 20:51
@Fattie yep. Which would suffice for the OP scenario. This function sets the top viewController. If you don't want that behavior, then you'd need a different function. – Elijah Jan 05 '18 at 22:14
1

Understood. nice stuff. – Fattie Jan 06 '18 at 01:39

Li Jin · Answer 9 · 2020-12-11T17:51:35.863

Swift 5 UINavigationController extension, which supports Fade animation as well when replacing.

extension UINavigationController {
    func find(of type: UIViewController.Type) -> UIViewController? {
        for controller in self.viewControllers {
            if controller.isKind(of: type) {
                return controller
            }
        }
        return nil
    }
    
    func go(to controller: UIViewController, animated: Bool = true) {
        if let old = self.find(of: type(of: controller)) {
            self.popToViewController(old, animated: animated)
        }
        else {
            self.pushViewController(controller, animated: animated)
        }
    }
    
    fileprivate func prepareFade() {
        let transition: CATransition = CATransition()
        transition.duration = 0.3
        transition.type = CATransitionType.fade
        view.layer.add(transition, forKey: nil)
    }
    
    func replace(to controller: UIViewController, animated: Bool = true, fade: Bool = true) {
        guard let current = self.topViewController else {
            return
        }
        
        var controllers = self.viewControllers
        controllers.remove(current)
        controllers.append(controller)
        
        if fade {
            prepareFade()
            self.setViewControllers(controllers, animated: false)
        }
        else {
            self.setViewControllers(controllers, animated: animated)
        }
    }
}

extension Array where Element: Equatable {
    mutating func remove(_ element: Element) {
        if let index = self.firstIndex(of: element) {
            self.remove(at: index)
        }
    }
}

score 0 · Answer 10 · answered Apr 15 '21 at 11:14

Often you need to clear the stack to your "Base", and put the new one on:

This answer from @duan is perfect and will literally replace the top item with a new item:

extension UINavigationController {
    func replaceTopViewController(with vc: UIViewController, animated: Bool) {
        var vcs = viewControllers
        vcs[vcs.count - 1] = vc // NB watch for bizarre zero size
        setViewControllers(vcs, animated: animated)
    }
}

However very often, you'll have a "Base" controller which you want to always be there.

If you want to clear everything safely to the Base and change to the new one (WITHOUT viewWillAppear running in Base), then:

extension UINavigationController {
    func popToRoot(andPushOnly: UIViewController) {
        var vcs = viewControllers
        while vcs.count > 1 { vcs.removeLast() }
        if vcs.count < 1 { return }
        vcs.append(andPushOnly)
        setViewControllers(vcs, animated: false)
    }
}

Replace a UIViewController in the UINavigationController hierarchy

10 Answers10

Often you need to clear the stack to your "Base", and put the new one on:

Linked