为什么要使用结构的对话框拨打对话框丢弃此例外？

Question

我试图重定向在结构中解码的 API 调用的输出，但是当我尝试使用数据创建对话框时，它给了我这个奇怪的异常。如您所见，API 返回数据，但仅当我创建对话框时我才会看到此异常。你能帮助我吗？

代码：

struct rspServerInfo: Codable{
        let ok: Bool
        let info: String
    }
    @IBAction func backendDetails(_ sender: Any) {
        
        guard let url = URL(string: "http://\(hostname):\(port)/STOInfo/ServerInfo")else{
            return
        }

        var request = URLRequest(url: url)
        request.httpMethod = "POST"
        request.setValue("application/json", forHTTPHeaderField: "Content-Type")
        let body: [String: AnyHashable] = [
            "username": username,
            "password": password,
        
        ]
        
        request.httpBody = try? JSONSerialization.data(withJSONObject: body, options: .fragmentsAllowed)
        let task = URLSession.shared.dataTask(with: request) {data, _, error in
            
            guard let data=data, error == nil else{
                return
            }
            do{
                let response = try JSONDecoder().decode(rspServerInfo.self, from: data)
                print("SUCCESS: \(response)")
                let dialogMessage = UIAlertController(title: "Backend details", message: response.info, preferredStyle: .alert)
                    let ok = UIAlertAction(title: "OK", style: .default, handler: { (action) -> Void in
                         print("Ok button tapped")
                    })
                dialogMessage.addAction(ok)
                self.present(dialogMessage, animated: true, completion: nil)
            }
            catch{
                print(error)
                let dialogMessage = UIAlertController(title: "Backend details", message: "Error retreiving.", preferredStyle: .alert)
                    let ok = UIAlertAction(title: "OK", style: .default, handler: { (action) -> Void in
                         print("Ok button tapped")
                    })
                dialogMessage.addAction(ok)
                self.present(dialogMessage, animated: true, completion: nil)
            }
        }
        task.resume()
    }

Answer 1

错误消息给出了一个很大的线索：

由于未被发现的例外，终止应用程序
“ nsinternalinconsistencyException”，原因：'对
布局引擎不得从背景线程执行
已从主线程访问。终止于未被发现
类型NSexception

例外

urlrequest在背景线程（包括其完成处理程序）上不同步运行。您（通常）无法在主线程之外进行UI工作。要显示结果，您需要将操作重新推回主线程：

DispatchQueue.main.async {
   // do UI work
}