ios - 从抛出函数类型 (_,_,_) throws 到非抛出函数类型 (Data?, Response?, URLResponse?) 的无效转换 Void

Question

我是 Swift 编程的新手，我在“let task = URLSession”上遇到错误。我研究并发现了其中一些错误，但没有一个答案对我有用。这是我的代码，第 44 行抛出这个错误

import UIKit

class loginViewController: UIViewController {

    @IBOutlet weak var userLoginTextField: UITextField!
    @IBOutlet weak var userPasswordTextField: UITextField!


    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    @IBAction func loginButtonTapped(_ sender: Any) {

        let user_login = userLoginTextField.text;
        let user_passwd = userPasswordTextField.text;

        if((user_passwd?.isEmpty)! || (user_passwd?.isEmpty)!) { return; }

        //Send user data to server
        let myUrl = NSURL(string: "https://www.pcpusa.net/legacy/iOS/userLogin.php");
        var request = URLRequest(url: myUrl! as URL);
        request.httpMethod = "POST";

        let postString = "login=\(String(describing: user_login))&password=\(String(describing: user_passwd))";

        request.httpBody = postString.data(using: String.Encoding.utf8);

        **let task = URLSession.shared.dataTask(with: request){**
            data,response,error in
            if error != nil {
                print("error=\(String(describing: error))")
                return
            }

            var err: NSError?
            var json = try JSONSerialization.JSONObjectWithData(data, options: .mutableContainers, error: &err) as? NSDictionary

            if let parseJSON = json {
                var resultValue:String = parseJSON["status"] as String!;
                print("result: \(resultValue)")

                if(resultValue=="Success")
                {

                    //Login is successful
                    NSUserDefaults.standardUserDefaults().setBool(true, value(forKey: "isUserLoggedIn"));
                    NSUserDefaults.standardUserDefaults().synchronize();

                    self.dismissViewControllerAnimated(true, completion:nil);

                }

            }

        }
        task.resume()
    }
}

Answer 1

URLSession.dataTask期望一个非抛出的完成处理程序，并且您正在向它传递一个抛出的闭包。因此，它无法推断方法(换句话说:它找不到具有该名称的方法接受抛出的闭包)。

要解决此问题，您应该捕获并处理解码 JSON 时可能发生的错误。