Introduction

In a Swift application using UIKit, the AppDelegate plays a crucial role in launching the app and setting up the main window. One important task is setting the initial view controller, which serves as the starting point for the user interface of the application. This process involves configuring the window and making key decisions about which view controller to display first.

Understanding the Application Lifecycle

When an iOS application launches, the system calls several methods in the AppDelegate class to set up the app's environment. Among these methods, application(_:didFinishLaunchingWithOptions:) is particularly important as it signals that the app has nearly completed its launching process.

Setting the Initial ViewController

To set the initial view controller in AppDelegate , you primarily interact with the UIWindow object. Here’s a technical breakdown of the steps involved:

1. Create a UIWindow instance: The application’s main window is an instance of UIWindow, and you need to create and assign this window to the app's window property.
2. Choose the Root ViewController: Decide which view controller should be the initial interface that the user sees. This could be a UIViewController , UINavigationController , or any custom controller you've created.
3. Configure the Root ViewController: Initialize the root view controller and assign it as the root for the window. This setup might also include setting up navigation stacks, tab bars, or other controller hierarchies.
4. Make the Window Key and Visible: Finally, call makeKeyAndVisible() on the window to display it and receive user interactions.

Below is a Swift code example demonstrating these steps in AppDelegate :

• Storyboard Support:
• Conditional Initial View Controllers:
• SceneDelegate for Modern iOS Apps: