UIViewController viewWillAppear not called when adding as subView

Question

I have a UIViewController that I am loading from inside another view controller and then adding its view to a UIScrollView.

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Answer 1

I can't understand your questions and your description. My problem was similar to this only.

CustomTabBarController -> CustomUINavigationController -> RootViewcontroller

viewWillAppear of CustomUINavigationController and RootViewController are not getting called unless you switched to another tab and come back.

The solution is call super.viewWillAppear(animated: true)

override func viewWillAppear(_ animated: Bool) {
    **super.viewWillAppear(true)**
}

I struggled for more than a day for this small mistake.

Answer 2

By default, appearance callbacks are automatically forwarded to children. It's determined with shouldAutomaticallyForwardAppearanceMethods property. Check value of this propery, if it's NO and if your child viewController should appear right on container's appearance, you should notify child with following methods in container's controller life-cycle implementation:

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    for (UIViewController *child in self.childViewControllers) {
        [child beginAppearanceTransition:YES animated:animated];
    }
}

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];
    [self.child endAppearanceTransition];
}

- (void)viewWillDisappear:(BOOL)animated {
    [super viewWillDisappear:animated];
    for (UIViewController *child in self.childViewControllers) {
        [child beginAppearanceTransition:NO animated:animated];
    }
}

- (void)viewDidDisappear:(BOOL)animated {
    [super viewDidDisappear:animated];
    [self.child endAppearanceTransition];
}

Customizing Appearance and Rotation Callback Behavior

Fixed my problem! Hope it would be helpful.