Question

这是我的情景。我从openweather开始使用json api，然后创建一个带有一些属性的类Weather。在Weather天气实体中，我创建了一个名为downloadWeather的函数来实际解析api然后我允许解析的值保存在属性中。

例如，self.max_temp = valueParsedFromJSON。然后在MainViewController中，在ViewDidload中，我创建一个Weather的实例，即天气，调用函数downloadWeather，然后更新与weather.somproperty对应的ui标签。下载的内容打印到控制台（仅用于调试）很好，但它根本不会将内容呈现到ui中。是什么原因？这是我的实际代码：

var currentWeather:CurrentWeather!
    // in MainViewControler.swift
    // create weather instance to call downloadWeatherDetails function
    override func viewDidLoad() {
        super.viewDidLoad()
        tableView.delegate = self
        tableView.dataSource = self

        currentWeather = CurrentWeather()
        let completed = currentWeather.downloadWeatherDetails()
        if completed == "completed" {
            self.updateUI()
        }
    }

class CurrentWeather {
    // this is CurrentWeather.swift where I save all the information in itself
    var _cityName:String!
    var _date:String!
    var _weatherType:String!
    var _currentTemp:Double!

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

    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
    }

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

    var currentTemp: Double {
        if _currentTemp == nil {
            _currentTemp = 0.0
            return _currentTemp
        }
        return _currentTemp
    }

    func downloadWeatherDetails(/*completed: DownloadComplete*/) -> String {
        let currentWeatherURl:URL = URL(string: current_weather_url)!
        Alamofire.request(currentWeatherURl).responseJSON { response in
            let result = response.result
            if let dict = result.value as? Dictionary<String, AnyObject> {
                if let main = dict["main"] as? Dictionary<String, AnyObject> {
                    if let currentTempInKev:Double = main["temp"] as? Double {
                        let currentTempInCel = Double(round(currentTempInKev - 273.15))
                        self._currentTemp = currentTempInCel

                    }

                }

                if let weatherArr = dict["weather"] as? [Dictionary<String, AnyObject>] {
                    if let main = weatherArr[0]["main"] as? String {
                        self._weatherType = main.capitalized
                    }                                       
                }

                if let name = dict["name"] as? String {
                    self._cityName = name                    
                }                
            }
            print(self.currentTemp)
            print(self.weatherType)
            print(self.cityName)
        }
        return "completed"
    }
    // the above works fine, but when called in MainViewController, properties is not rendered into UI
}

Answer 1

要更新UI，您需要在主线程中设置UI控件的属性。 Alamofire方法本质上是异步的，并且不会阻止主UI线程。将更新UILabels等的代码放在

中

DispatchQueue.main.async { }

它应该有效

来自JSON的内容实际上并未呈现为UI

1 个答案: