Understanding UIViewController’s viewIsAppearing(_:)

https://developer.apple.com/documentation/uikit/uiviewcontroller/4195485-viewisappearing

Background

Common UIViewController lifecycle management methods are viewDidLoad(), viewWillAppear(_:), viewDidAppear(_:), viewWillDisappear(_:), and viewDidDisappear(_:). Each serves a specific purpose and provides developers the opportunity to perform tasks at appropriate times.