我使用以下代码从php页面检索响应 . 它的工作正常，除了每隔一段时间它在接收到以下行的零值后崩溃并出现错误：
let responseString = NSString（data：data！，encoding：String.Encoding.utf8.rawValue）
有没有办法可以 grab 这个？
let myUrl = NSURL(string: "https://*****backend/newmessage.php")
let request = NSMutableURLRequest(url: myUrl! as URL)
request.httpMethod = "POST"
let postString = "userid=\(userid!)"
print(postString)
request.httpBody = postString.data(using: String.Encoding.utf8)
let task = URLSession.shared.dataTask(with: request as URLRequest) {
data, response, error in
DispatchQueue.global(qos: DispatchQoS.QoSClass.default).async {
let responseString = NSString(data: data!, encoding: String.Encoding.utf8.rawValue)
if error != nil {
print("Error: \(error)")
}
DispatchQueue.main.async() {
print(responseString!)
if (responseString! == "NEW"){
self.messageIcon.setImage(UIImage(named: "newmessage.png"), for: UIControlState.normal)
}else{
self.messageIcon.setImage(UIImage(named: "envelope.png"), for: UIControlState.normal)
}
}
}
}
task.resume()
1 回答
为什么不用
if-else声明来解决潜在的问题呢？或者，您可以使用guard语句 .if responseString != nil { // do stuff } else { // do other stuff}