php - iOS 应用程序接收格式正确的 JSON，但仍然返回为不以数组或对象开头

Question

所以基本上我的服务器上有一个登录脚本，它根据用户凭据是否正确或错误返回结果，并且我有一个 iOS 应用程序将数据发送到该登录脚本以返回正确或错误的结果。

这是我的登录页面的相关部分，显示返回代码($userDetails 是正确或错误凭据的 TRUE 或 FALSE 检查):

$userDetails = $dao->getUserDetailsWithHashedPassword($email,$password);
if($userDetails===TRUE) {
    $returnValue["status"] = "Success";
    $returnValue["message"] = "User logged in !";
    echo json_encode($returnValue);
} else {
    $returnValue["status"] = "error";
    $returnValue["message"] = "User not found";
    echo json_encode($returnValue);
}

如果有人需要查看 getUserDetailsWithHashedPassword() 的作用，click here

使用 Postman 测试 HTTP POST，一切正常，在正文中发布 email@email.com 和 testpassword 并使用正确的 Content-Type (application/x-www-form-urlencoded) 时，我得到了正确的结果:

{"status":"error","message":"User not found"}

现在我的 iOS 应该用这段代码来解释它:

@IBAction func loginButtonPressed(_ sender: AnyObject) {
        let userEmail = emailLoginField.text
        let userPassword = passwordLoginField.text
        // Check for empty fields
        if((userEmail?.isEmpty)! || (userPassword?.isEmpty)!) { 
            // Display alert message
            displayMyAlertMessage(userMessage: "All fields are required");     
            return ;
        }
        // Send user data to server side
        let myUrl = URL(string: "https://support.vincentsolutions.ca/userLogin.php");
        var request = URLRequest(url:myUrl!);
        request.httpMethod = "POST";
        request.addValue("application/x-www-form-urlencoded", forHTTPHeaderField: "Content-Type")
        let postString = "email=\(userEmail!)&password=\(userPassword!)";
        request.httpBody = postString.data(using: String.Encoding.utf8);

        URLSession.shared.dataTask(with: request, completionHandler: { (data:Data?, response:URLResponse?, error:Error?) -> Void in
            if error != nil {
                print ("error=\(error)")
                return
            }
            do {
                let json = try JSONSerialization.jsonObject(with: data!, options: .mutableContainers) as? NSDictionary
                if let parseJSON = json {
                    var resultValue = parseJSON["status"] as? String
                    print("result: \(resultValue)")
                    var isUserLoggedIn:Bool = false;
                    if(resultValue=="Success") {
                        // Login is successful
                        UserDefaults.standard.set(true, forKey: "isUserLoggedIn");
                        UserDefaults.standard.synchronize();    
                        self.performSegue(withIdentifier: "loginSuccesful", sender: self)
                    }
                    var messageToDisplay:String = parseJSON["message"] as! String!;
                    if(!isUserLoggedIn) {
                        messageToDisplay = parseJSON["message"] as! String!;
                    }
                    DispatchQueue.main.async(execute: {
                        // Display alert message with confirmation.
                        var myAlert = UIAlertController(title: "Alert", message: messageToDisplay, preferredStyle: UIAlertControllerStyle.alert);

                        let okAction = UIAlertAction(title: "Ok", style: UIAlertActionStyle.default){ action in
                            self.dismiss(animated: true, completion: nil);
                        } 
                        myAlert.addAction(okAction);
                        self.present(myAlert, animated: true, completion: nil);
                    });   
                }  
            } catch let error as NSError {
                print("An error occured: \(error)")
            }
        }).resume()

现在，当我从 iOS 应用程序运行代码时，出现此错误:

An error occured: Error Domain=NSCocoaErrorDomain Code=3840 "JSON text did not start with array or object and option to allow fragments not set."

有人看出这里出了什么问题吗？我尝试在此处和互联网上查找该错误，但找不到与我的情况相关的任何内容。

Answer 1

这是因为您从 URL 收到的响应可能不是正确的 JSON 格式。我建议你做两件事 -

1. 尝试 NSLog 数据和响应
2. 试试这个

让 json = 尝试 NSJSONSerialization.JSONObjectWithData(data!, options: NSJSONReadingOptions.AllowFragments) 作为! NS字典