UIApplication.sharedApplication not available

I'm trying to get a reference to my app delegate from a UIViewController but I keep getting an this error message:

'sharedApplication()' is unavailable: Use view controller based solutions where appropriate instead.

I've been reading all the articles dealing with this kind of message but my problem seems unrelated as I'm not using any third party framework. While a Today Extension is part of my app, the class in which the error occurs is totally unrelated. I even created a completely new class and keep getting the same error:

When I do the same thing in a playground it works fine. What am I missing?

Problem solved. I've been to the Build Settings of my app again and stumbled over

Require Only AppExtension-Safe API

all set to YES. The default though is NO. When I set this to NO the error disappeared.

I sure don't remember ever touching or even knowing about this but luckily now it works.