Compile-time test for availability of UIApplication.shared? - ios

Question

I have some shared code that needs to work in both iOS apps and app extensions, and needs to set UIApplication.shared.isNetworkActivityIndicatorVisible — but only if the code is used in an app.
In an app extension, UIApplication.shared gives this compile error:
'shared' is unavailable: Use view controller based solutions where appropriate instead
That’s fine; I don’t want to use it in the app extension. However, I’m unable to find a way to disable that code at compile time. Sadly, if #available doesn’t seem to do the trick; it shuts off the code path, but the compiler still doesn’t like it:
if #available(iOSApplicationExtension 0, *) {
print("This is an extension")
} else {
print("This is an app")
print(UIApplication.shared) // Unreachable in extension, but still doesn’t compile
}
I don’t see any #if check that handles this.
Is there any way in Swift to conditionally compile the code that requires UIApplication.shared?

Answer 1

A possible solution is to avoid explicit usage of UIApplication.shared and use Objective-C selector wrap instead.
Here is an extension that might help (based on https://github.com/ephread/Instructions/issues/21)
extension UIApplication {
static var safeShared: UIApplication? {
guard UIApplication.responds(to: Selector(("sharedApplication"))) else {
return nil
}
guard let unmanagedSharedApplication = UIApplication.perform(Selector(("sharedApplication"))) else {
return nil
}
return unmanagedSharedApplication.takeRetainedValue() as? UIApplication
}
}
Usage
if let app = UIApplication.safeShared {
result = app.applicationState == .active
}
Happy Coding 👨‍💻