How can we handle changes in our application’s lifecycle state? (SwiftUI)

Sources & Resources

Main Source: 🔗 The Ultimate Guide to the SwiftUI 2 Application Life Cycle

Additional Sources:

• 🔗 Apple Developer Documentation - App

Further Reading:

• 🔗 Managing App Life Cycle with SwiftUI

TL/DR

In SwiftUI, you manage the application’s lifecycle using the @Environment(\.scenePhase) property, along with onAppear and onDisappear modifiers. The scenePhase property allows you to monitor and respond to changes in the app's lifecycle state.

SwiftUI introduces a declarative way to manage an application's lifecycle without relying on the traditional AppDelegate. Instead, you use the App protocol and the scenePhase environment property to track and respond to changes in the app's state.

Here are the key components:

• @Environment(\.scenePhase): Provides access to the current lifecycle state of the app, which can be .active, .inactive, or .background.

• onAppear(perform:): This modifier is used to run code when a view appears on the screen.

• onDisappear(perform:): This modifier allows you to execute code when a view disappears from the screen.

• App Lifecycle States:

  • .active: The app is currently active and in the foreground.
  • .inactive: The app is transitioning or is temporarily in an inactive state.
  • .background: The app is running in the background.

Example SwiftUI Code

import SwiftUI

@main
struct MyApp: App {
    @Environment(\.scenePhase) var scenePhase

    var body: some Scene {
        WindowGroup {
            ContentView()
                .onAppear {
                    // Handle view appearance
                }
                .onDisappear {
                    // Handle view disappearance
                }
        }
        .onChange(of: scenePhase) { newPhase in
            switch newPhase {
            case .active:
                // The app is active
                print("App is active")
            case .inactive:
                // The app is inactive
                print("App is inactive")
            case .background:
                // The app is in the background
                print("App is in the background")
            @unknown default:
                // Handle unexpected new phases
                break
            }
        }
    }
}

Additional Details

SwiftUI’s declarative lifecycle management allows for a more integrated approach to handling the state of your app, removing the need for a separate AppDelegate in most cases. However, you can still integrate an AppDelegate if needed, using the UIApplicationDelegateAdaptor property wrapper to bridge between UIKit and SwiftUI.

In Bullets

• Lifecycle Management: In SwiftUI, use the @Environment(\.scenePhase) property to track app state changes.
• Declarative Modifiers: Use onAppear and onDisappear to manage view-specific lifecycle events.
• Integrated Handling: Most lifecycle management can be handled within the SwiftUI App protocol, reducing the need for an AppDelegate.
• State Monitoring: The scenePhase provides a straightforward way to monitor .active, .inactive, and .background states.