Is it possible to create a custom application by extending the UIApplication class?

In iOS development, the UIApplication class represents the central object of the application, managing its lifecycle and interaction with the system. Although technically possible to create a subclass of UIApplication, this is rarely done and not recommended without a compelling reason.

Apple provides the option to specify your own subclass of UIApplication in the UIApplicationMain function, but most often it is sufficient to use the standard class and extend functionality through the application delegate (UIApplicationDelegate).

Creating your own subclass of UIApplication is justified if you need to change behavior at the application level, for example, to handle system-level events that are not accessible through the delegate. However, this requires a deep understanding of iOS internals and can lead to compatibility issues.

Example of specifying a custom subclass of UIApplication:

UIApplicationMain(
    CommandLine.argc,
    CommandLine.unsafeArgv,
    NSStringFromClass(MyCustomApplication.self),
    NSStringFromClass(AppDelegate.self)
)

Where MyCustomApplication is your subclass of UIApplication.

In most cases, it is enough to use the standard UIApplication and extend logic through the delegate.