ChildViewController viewDidAppear before PageViewController's viewWillAppear

[ChristianSteffens]

I noticed a strange behaviour that caused us quiet some headaches: The very first child ViewController of the Page(Boy)ViewController gets 'presented' before the 'parent' controller has appeared on screen.

I added some print statements to the example project: https://github.com/hibento/Pageboy/tree/feature/Appearance

Here's an example run:

1. viewDidLoad for the Page(Boy)ViewController ✔️
2. viewDidLoad for the ChildViewController (with ID 0D2C7 ...) ✔️
3. viewWillAppear for the ChildViewController ❌
4. viewDidAppear for the ChildViewController
5. viewWillAppear for the Page(Boy)ViewController
6. viewDidAppear for the Page(Boy)ViewController

viewDidLoad
viewDidLoad 0D2C7F77-A822-4EF7-A0DA-D4C91F71B118
viewWillAppear 0D2C7F77-A822-4EF7-A0DA-D4C91F71B118
viewDidAppear 0D2C7F77-A822-4EF7-A0DA-D4C91F71B118
viewWillAppear
viewDidAppear

I find this very confusing: How can the ChildViewController' enter viewDidAppear before the PageBoyViewController has entered this state or at at least would follow the ChildViewController's entering of this state immediately.