[matthewmacleod]

@UIApplicationMain is the key there, from what I can see. An Objective C iOS app typically includes a main.m entry point which calls UIApplicationMain and passes the AppDelegate. This seems to have been removed in favour of what Swift is calling a "declaration attribute", which presumably does the same thing.

In this sense, the code is even less clear than the Objective C implementation.

[sAuronas]

They removed the need for main by making global scope the entry point.