在演示过程中尝试呈现UIAlaerController

Question

/*
 // api end point to use when user try to login
 // param : email ; User Entered Email
 // param : password ; User Entered Password

*/
func loginUserInterface(params : [String : String],completion: @escaping StringCompletion)
{
    let url = baseURL + APIManager.loginUserEndPoint
    print(url)
    Alamofire.request(url, method: .post, parameters: params).responseJSON{
        response in
        if response.result.isSuccess{
            let JSONString : JSON = JSON(response.result.value!)
            let code = response.response?.statusCode
            if (code == 401)
            {
                completion(false,JSONString,401)
            }
            else {
                completion(true,JSONString,code!)
            }



        }
        else{
            let errorJSON: JSON = JSON(response.result.error!)
            completion(false,errorJSON,503)
        }
    }
}

登录用户界面方法来自API管理器。

从loginUser()调用功能ViewController。

func loginUser()
{
    showLoader()
    let params : [String : String] = ["email" : loginEmailTF.text!, "password" : loginPasswordTF.text!]
    APIManager.sharedInstance.loginUserInterface(params: params){ (success, data, statusCode) in
        self.hideLoader()
        if success {
            print(data)
        }
        else
        {
            print(statusCode)
            switch statusCode
            {
            case 401:
                self.showInfo(title: "Error", message: "Incorrect Email or password")
                break
            case 404:
                self.showInfo(title: "Error", message: "No Response from server, Please try again later")
                break
            case 500:
                self.showInfo(title: "Error", message: "No Response from server, Please try again later")
                break
            case 503:
                self.showInfo(title: "Error", message: "No Active Internet Connection")
                break

            default:
                self.showInfo(title: "Error", message: "No Response from server, Please try again later")
            }

        }
    }


}

功能showInfo()

    func showInfo(title: String, message: String)
{
    let alert2 = UIAlertController(title: title, message: message, preferredStyle: .alert)
    let okAction = UIAlertAction(title: "Ok", style: .default) {
        (UIAlertAction) in
        alert2.dismiss(animated: false, completion: nil)
    }
    alert2.addAction(okAction)
    self.present(alert2, animated: false, completion: nil)
}

功能showLoader()

func showLoader()
{
    let loadingIndicator = UIActivityIndicatorView(frame: CGRect(x: 10, y: 5, width: 50, height: 50))
    loadingIndicator.hidesWhenStopped = true
    loadingIndicator.style = UIActivityIndicatorView.Style.gray
    loadingIndicator.startAnimating();

    alert.view.addSubview(loadingIndicator)
    present(alert, animated: false, completion: nil)
}

功能hideLoader()

func hideLoader()
{
    alert.dismiss(animated: false, completion: nil)
}

注]当状态代码为401时，loader和showInfo都可以正常工作。但是当状态代码为503时，我会收到以下警告。

2019-10-07 16：56：45.069579 + 0500定义的形状[1859：827702]无法结束BackgroundTask：不存在标识符为1（0x1）的后台任务，或者它可能已经结束了。打破UIApplicationEndBackgroundTaskError（）进行调试。

XCode版本10.1（10B61）Swift 4.2

Answer 1

无法结束BackgroundTask：不存在标识符为1（0x1）的后台任务，或者它可能已经结束。中断UIApplicationEndBackgroundTaskError（）以进行调试。

这只是弹出的一则令人讨厌的控制台消息。忽略它。它不会影响代码的功能。