iOS - UI标签未更新

Question

我正在尝试使用AlamoFire构建一个天气应用程序，我得到了预期的JSON响应，但当我试图将日期更新为UI标签时，我的变量返回了一个nil。如果有人有机会让我知道我哪里错了

import UIKit

class WeatherVC: UIViewController {
    @IBOutlet weak var dateLbl: UILabel!

    @IBOutlet weak var weatherType: UILabel!
    @IBOutlet weak var cityname: UILabel!
    @IBOutlet weak var currentTemp: UILabel!

    var  weatherConstants = WeatherConstant()

    override func viewDidLoad() {
        super.viewDidLoad()
       // updateUI()
//
        weatherConstants.downloadCurrentWeather {

self.updateUI()

        }

        weatherConstants = WeatherConstant()
        print(Current_Weather_Url)


    }


    func updateUI() {

            weatherType.text = weatherConstants.weatherType
            cityname.text = weatherConstants.cityName


        print("current city name is \(weatherConstants.weatherType)")
    }



}

天气常量

import UIKit
import Alamofire


class WeatherConstant {
    var  _cityName :String!
    var _currentTemp : Double!
    var _weatherType : String!
    var _highTemp : String!
    var _date :String!




    var cityName :String {
        if _cityName == nil {
            _cityName = ""
        }
        return _cityName
    }

    var currentTemp : Double{

    if _currentTemp == nil {
    _currentTemp = 0.0
        }
        return _currentTemp

    }

    var weatherType : String {
        if _weatherType == nil {
            _weatherType = ""
        }
        return _weatherType
    }
    var highTemp : String {
        if _highTemp == nil {
        _highTemp = ""
    }
        return _highTemp
}

    var date : String {
        if _date == nil {
            _date = ""
        }
        let dateFormatter = DateFormatter()
        dateFormatter.dateStyle = .long
        dateFormatter.timeStyle = .none

        let currentDate = dateFormatter.string(from: Date())

        self._date = "Today, \(currentDate)"
        return _date
}
    //func downloadWeatherDetails(completed : DownloadComplete) ===> downloadWeatherDetails(completed : @escaping DownloadComplete)


    func downloadCurrentWeather(completed: @escaping DownloadComplete) {
        Alamofire.request(Current_Weather_Url).responseJSON{ response in

            let result = response.result
           // print(result)
              debugPrint(result)

            if let dict = result.value as? Dictionary<String, AnyObject>{
                if let name = dict["name"] as? String {
                    self._cityName = name
                    print("current name is \(self._cityName)")
                }

                if let currentTemp = dict["weather"] as? [Dictionary<String, AnyObject>] {
                    if let main = currentTemp[0]["main"] as? String{
                        self._weatherType = main
                        print("Current Weather Type \(self._weatherType)")

                    }
                }

            }
            completed()

        }

    }




}

JSON响应

https://samples.openweathermap.org/data/2.5/weather?lat=35&lon=139&appid=e9a34088739f38c517b4a45084f5ed82
SUCCESS: {
    base = stations;
    clouds =     {
        all = 0;
    };
    cod = 200;
    coord =     {
        lat = "35.02";
        lon = "139.01";
    };
    dt = 1485792967;
    id = 1907296;
    main =     {
        "grnd_level" = "1013.75";
        humidity = 100;
        pressure = "1013.75";
        "sea_level" = "1023.22";
        temp = "285.514";
        "temp_max" = "285.514";
        "temp_min" = "285.514";
    };
    name = Tawarano;
    sys =     {
        country = JP;
        message = "0.0025";
        sunrise = 1485726240;
        sunset = 1485763863;
    };
    weather =     (
                {
            description = "clear sky";
            icon = 01n;
            id = 800;
            main = Clear;
        }
    );
    wind =     {
        deg = 311;
        speed = "5.52";
    };
}

当前天气类型可选(“Clear”)->这是我试图提供给UIlabel的天气类型

当前城市名称是可选的(“”)->这里我尝试打印UILabel中的数据，但返回的是空字符串

2018-08-07 11:18:09.567868-0700WeatherApp1.182321:3248301函数boringssl_session_errorlog:第2881行boringssl_session_read SSL_ERROR_ZERO_RETURN(6)：操作失败，因为连接已被干净地关闭并显示close_notify警报

Answer 1

您正在用viewDidLoad中的新对象覆盖weatherConstants值。试着去掉它。

(更长的解释:您正确地创建了一个weatherConstants对象，并请求它获取数据。但在此过程中，您创建了该对象的第二个实例，该实例将覆盖第一个实例。因此，当第一个实例完成网络请求并告诉您的UI重绘时，UI从第二个WeatherConstants实例获取数据)