didFinishLaunchingWithOptions

didFinishLaunchingWithOptions is an optional method in the UIApplicationDelegate protocol. It is called by the system after the app has been launched and initialized, but before the user interface is presented. The method receives the application instance and a dictionary of launchOptions describing why the app was started, and it returns a Boolean value indicating whether the app finished launching successfully.

Purpose and typical use: Use this method to perform one-time or global setup for the entire app, such as configuring services, registering for push notifications, restoring state, initializing analytics, and preparing shared resources. Because user interface setup is often handled by scene-based lifecycles in newer iOS versions, the work here should focus on app-wide initialization rather than creating UI elements.

Launch options: The launchOptions dictionary can carry keys that describe the launch reason, including cases such as a remote notification (UIApplication.LaunchOptionsKey.remoteNotification), a URL that opened the app (UIApplication.LaunchOptionsKey.url), a location update, or a user activity. The exact keys may vary by iOS version and context.

Lifecycle context: Starting with iOS 13, Apple introduced a scene-based lifecycle. In apps that use scenes, didFinishLaunchingWithOptions is still called during launch, but much of the UI lifecycle is managed by SceneDelegate (for example, scene:willConnectToSession:options:). The method remains suitable for global initialization and configuration that should occur regardless of which scene is presented.

Return value and best practices: Return true to indicate successful launch. Keep work here brief and synchronous where possible, and defer long-running tasks or heavy UI setup to appropriate lifecycle methods or background processing. Use the launchOptions to tailor initial setup based on how the app was launched.