Function signature specialization crash in swift

Question

I am getting crash reports from our users but I didn't understand the crash report.

It says:

Ribony: function signature specialization <Arg[0] = Owned To Guaranteed and Exploded, Arg[1] = Owned To Guaranteed and Exploded, Arg[2] = Owned To Guaranteed and Exploded, Arg[3] = Exploded, Arg[4] = Owned To Guaranteed> of Ribony.ChatManager.sendMessage (Ribony.ChatManager)(Swift.String, to : Swift.String, anonClosed : Swift.String, toWeb : Swift.Int) -> () + 3608

I am using swift. What is this report? My sendMessage method:

func sendMessage(message: String,to: String,anonClosed: String,toWeb: Int) {
        NSNotificationCenter.defaultCenter().postNotificationName(mySpecialNotificationKey, object: self,userInfo:["message":message])
        var sender=""
        var token=""
        var toSubstr=""
        if count(to) >= 5 {
            let rangeOfTo = Range(start: to.startIndex,
            end: advance(to.startIndex, 5))
            toSubstr = to.substringWithRange(rangeOfTo)
        }else{
            toSubstr=to
        }
        socket.emit("sendMessage","ok")
}

How can I resolve it?

Answer 1

You need to look at what the actual exception is. The most common is "unexpectedly found nil while unwrapping an Optional Value" which would suggest that you're passing a String! to this method that was really nil. But you need to start by looking at the exception message, not just the crash stack.

Answer 2

Taken from here: https://forums.developer.apple.com/thread/6078

The message seems to correlate with passing a nil object to a swift function that expects non-nil object.

So change your function signature to: func sendMessage(message: String?,to: String?,anonClosed: String?,toWeb: Int?) or make sure it gets called with non-nil objects from Objective C