What Is AppDelegate and What Do You Need to Add When Developing an App?

When creating an app for iOS, one of the key components you will encounter is the AppDelegate. It plays a vital role in managing how your app behaves throughout its life cycle. This article explains what the AppDelegate is and what you should add when developing an app.

What Is AppDelegate?

AppDelegate is a class in an iOS app that responds to events at the app level. It acts as a connection point between the operating system and your app. The system sends messages to the AppDelegate when certain things happen, such as when the app starts, moves to the background, or is about to be closed.

In simple terms, the AppDelegate is like the central controller of the app’s main events and states. It helps your app react to important changes big or small.

The Role of AppDelegate in an App

When you run an iOS app, the system creates the app and sets up the environment needed for it to work. The AppDelegate is involved in this process to configure the app’s initial state.

Here are some common tasks handled by the AppDelegate:

• Launching the App: Setting up the app as it starts, loading necessary resources.
• Handling App Life Cycle Events: Responding to events such as entering the background, becoming active again, or terminating.
• Managing Notifications: Handling notifications received by the app.
• Handling State Restoration: Saving and restoring the state of the app.
• Responding to External Events: Managing URL schemes, shortcuts, and other external inputs.

Basic Structure of AppDelegate

An AppDelegate usually inherits from UIResponder and adopts the UIApplicationDelegate protocol. This protocol defines several methods that you can implement to respond to the app life cycle events.

Here is a basic outline:

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What to Add When Developing an App

Developing an app requires adding the right code into the AppDelegate so your app works well and handles changes smoothly. Here are some common things to add:

1. Setup for App Launch

In the didFinishLaunchingWithOptions method, you usually set up the initial view controllers, configure services, and prepare any data or settings your app needs. This method is your starting point for what your app does when it opens.

2. Managing the App’s Life Cycle

Add code to pause tasks, save data, or release resources when the app moves to the background or closes. For example, pause timers or save user progress in applicationDidEnterBackground. Restore things to their working state in applicationDidBecomeActive.

3. Handling Notifications

If your app uses notifications, implement methods in AppDelegate to register for remote notifications and handle incoming notifications. This lets your app respond appropriately when a notification is received, whether the app is in the foreground or background.

4. Supporting Background Tasks

You can request extra time to complete tasks by adding code in the applicationDidEnterBackground method. This is useful for tasks like saving files or finishing network calls.

5. Managing URL Schemes and Deep Links

If your app needs to open from a URL or handle links, add code in AppDelegate methods related to URL opening. This lets users open parts of your app directly from external links.

6. State Restoration Support

To improve user experience, your app can save its state when it quits and restore it when reopened. Add code to save data and restore the interface in the appropriate AppDelegate methods.

7. Configuring Third-Party Services

If your app uses third-party libraries or services (like analytics or crash reporting), initialize them in didFinishLaunchingWithOptions. This ensures these services start correctly when the app launches.

The AppDelegate is an important part of every iOS app. It connects your app with the system and helps manage important events like launch, backgrounding, and termination. When developing an app, make sure to add code that configures your app on launch, handles life