Why doesn't cast work from NSData to String? Swift

Question

I have that code

func SendRequest(request: String) -> String
{
    var response = \"\"
    var (success, errmsg) = client.connect(timeout: 1)
    if succe         


        

Answer 1

Answering: "Sometimes, cast NSData to String doesn't work."
Not all data is convertible to a particular string encoding. In the case:

var str = String.init(data: bytes, encoding: NSUTF8StringEncoding)

there are a great number of bytes and byte sequences that have no valid UTF-8 character encoding.