24.6 Summary
SwiftUI provides a collection of modifiers designed to allow actions to be taken in the event of lifecycle changes occurring in a running app. The onAppear() and onDisappear() modifiers can be used to perform actions when a view appears or disappears from view within a user interface layout. The onChange() modifier, on the other hand, is useful for performing tasks each time the value assigned to a property changes.
The ScenePhase environment property, when used with the onChange() modifier, allows an app to identify when the state of a scene changes. This is of particular use when an app needs to know when it moves between foreground and background modes.
