Does a Completion Handler end the function?

Question

Perhaps I do not understand the concept of a completion handler, but I have a function like so;

func someFunction(completion: @escaping (Bool, LoginError?) -> Void) {
    self.checkDevice() { allowed, error in
       if let e = error {
          completion(false, e)
       }
        completion(true, nil)
    }
}

While being light on what checkDevice() does, the basic premise is that it performs an asynchronous network call, and returns either true with no error (nil), or returns false with an error.

When I run this code, I am finding that the completion handler is being called twice. It sends a completion as a tuple (as false, error) and also as (true, nil). I've done some debugging and there seems to be no manner in which someFunction() is called twice.

I was of the belief that once a completion is sent, the function would end. In my test case, I am forcing an error from checkDevice(), which should result in me sending the completion as (false, error), but I am seeing both (false, error) and (true, nil). Does a completion not immediately end the function?

Answer 1

A completion handler does not end a function. The typical way to end a function is to insert a return.

See comment re: your specific case