如何确定泛型是否在Swift中是可选的？

I want to extend an Array with a function that would return a count of all non-nil items in an Array. Ideally this would work with an array of any optional or non-optional types. I tried a variety of things that failed to compile, crashed Xcode or both. I would have assumed it would look something like this:I want to extend an Array with a function that