用于Swift的Facebook SDK为id而不是`“xx”返回可选（“xx”）

Question

我在swift 4中使用Facebook SDK。它返回optional("xx") userId而不是"xx"普通ID。我正在弄清楚如何从结果中提取值。

 let connection = GraphRequestConnection()
            var request = GraphRequest.init(graphPath: "me")
            request.parameters =     ["fields":"email,first_name,last_name,picture.width(1000).height(1000)"]


            connection.add(request, completion: {
                (response, result) in

                switch(result){
                case .success(let res):
                    print(res)

                        if let responseDictionary = res.dictionaryValue {
                            let id = responseDictionary["id"] as? String
                            print(id)
                            let first = responseDictionary["first_name"] as? String
                            print(first)
                            if let picture = responseDictionary["picture"] as? NSDictionary {
                                if let data = picture["data"] as? NSDictionary{
                                    if let profilePicture = data["url"] as? String {
                                        print(profilePicture)
                                    }
                                }
                            }
                        }
                    break
                case .failed(_):
                    break
                }

它将id打印为Optional("2013340245575263")