Determine if view that appears was pushed or came from back button in navigation bar

Question

Is there a way to tell if a new controller came from a navigation back button or was pushed onto the stack? Id like to reload data only for pushing on the navigation stack, not on a back button press.

score 24 · Accepted Answer · answered Dec 30 '13 at 23:36

24

As of iOS 5.0 you can do this:

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];

    if (self.isBeingPresented || self.isMovingToParentViewController) {
        // "self" is being shown for the 1st time, not because of a "back" button.
    }
}

answered Dec 30 '13 at 23:36

rmaddy

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3

This will not work if your view controller is the first view controller on tab of a tab bar controller. It will work the first time, but thereafter switching to it's tab will appear as if it was a back action because neither `isBeingPresented` nor `isMovingToParentViewController` will be true. Such a case is rare, but if this is your situation check out http://stackoverflow.com/a/40801594/5152481 – gwest7 Nov 25 '16 at 10:48
This does not seem to work in iOS10 - both isBeingPresented and isMovingToParentViewController are both false the first time my view controller is presented. – Kendall Helmstetter Gelner Dec 13 '16 at 22:17
@KendallHelmstetterGelner Are you calling those in `viewWill|DidAppear` or `viewWill|DidDisappear`? They only work in those 4 methods. – rmaddy Dec 13 '16 at 22:18
@maddy - Yes, I'm talking about the standard viewWillAppear: method. Both values on the current VC came up as false in iOS10. – Kendall Helmstetter Gelner Dec 26 '16 at 03:44

score 1 · Answer 2 · answered Dec 30 '13 at 23:17

1

If your push also includes instantiating the view controller, put your push-only logic in viewDidLoad. It will not be called on back because it has already been loaded.

answered Dec 30 '13 at 23:17

coneybeare

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Couldn't viewDidLoad be called on back if the view was unloaded due to memory pressure? – Stephen Johnson Dec 30 '13 at 23:26
depends if you unload it or not – coneybeare Dec 30 '13 at 23:27
You coudl set a bool ivar called instantiated, then set it to YES at the end of viewDidLoad. Once it is set to yes, don't do the thing you want to only happen once. – coneybeare Dec 30 '13 at 23:28

Ron · Answer 3 · 2013-12-30T23:40:07.733

You could implement the UINavigationControllerDelegate and override the `navigationController:didShowViewController:animated:' method. You'll then have to check the returned view controller to make a determination as to whether you came back from the expected view controller.

- (void)navigationController:(UINavigationController*)navigationController didShowViewController:(UIViewController*)viewController animated:(BOOL)animated
{
    if (yourPushedViewController == viewController)
    {
        // Do something
    }
}

Determine if view that appears was pushed or came from back button in navigation bar

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