Question

我目前正在使用Swift学习iOS开发。我正在制作一个简单的天气应用。我有几个按钮可以在接下来的4个小时内获得天气。我从黑暗的天空API获取天气，以JSON格式返回。我终于想出了如何从JSON中检索正确的数据，并创建了一个获取数据的类。

typealias WeatherCallback = (Weather) -> Void
typealias ErrorCallback = (Error) -> Void

class NetworkManager {

    class func getWeather(latitude: String, longitude: String, onSuccess: WeatherCallback? = nil, onError: ErrorCallback? = nil) {

        let urlString = "https://api.darksky.net/forecast/(api key)/" + latitude + "," + longitude + "?units=si"

        let url = URL(string: urlString)

        URLSession.shared.dataTask(with: url!) { (data, response, error) in
            if error != nil {
                print(error!)
                onError?(error!)
            } else {
                do {
                    let json  = JSON(data: data!)
                    let weather = Weather()

                    DispatchQueue.main.async {
                        weather.updateWithJSON(dict: json["currently"], hour: 0)

                        for i in 1...4 {
                            weather.updateWithJSON(dict: json["hourly"]["data"][i], hour: i)
                        }
                    }
                    onSuccess?(weather) 
                }
            }
            }.resume()
    }
}

我有一个不同的类来存储检索到的数据。

class Weather {

    public var currentTime: String = ""
    public var currentTemperature: String = ""

    public var nextHourTime: String = ""
    public var nextHourTemperature: String = ""

    public var nextTwoHourTime: String = ""
    public var nextTwoHourTemperature: String = ""

    public var nextThreeHourTime: String = ""
    public var nextThreeHourTemperature: String = ""

    public var nextFourHourTime: String = ""
    public var nextFourHourTemperature: String = ""

    func updateCurrentData(time: String, temp: String) {
        currentTime = time
        currentTemperature = temp
    }

    func updateWithJSON(dict: JSON, hour: Int){

        switch hour {
        case 0:
            currentTime = dict["time"].stringValue
            currentTemperature = dict["temperature"].stringValue

        case 1:
            nextHourTime = dict["time"].stringValue
            nextHourTemperature = dict["temperature"].stringValue

        case 2:
            nextTwoHourTime = dict["time"].stringValue
            nextTwoHourTemperature = dict["temperature"].stringValue

        case 3:
            nextThreeHourTime = dict["time"].stringValue
            nextThreeHourTemperature = dict["temperature"].stringValue

        case 4:
            nextFourHourTime = dict["time"].stringValue
            nextFourHourTemperature = dict["temperature"].stringValue

        default:
            print("rip")
        }
    }
}

我的问题是，我无法从Weather内访问班级ViewController中存储的值。

例如

let weather = Weather()

print(weather.currentTime)

任何指导我指向正确方向的帮助都会很棒！谢谢！

Answer 1

您可以通过创建Weather课程Singleton来完成此操作。使用单例只存在此对象的一个副本，并且状态可由任何其他对象共享和访问。

class Weather {
public static var sharedInstance =  Weather()
...
private init() {
}
}

并获得像这样的单身对象

let weather = Weather.sharedInstance // it will give you the same instance of Weather every time you call it.

Answer 2

您可以使用delegate pettern在viewcontroller中获取结果。首先创建一个类似的协议：

protocol YourDelegateProtocol {
    func getDataFromServer(data: String)
}

之后在NetworkManager类中创建此协议的实例，如下所示：

class NetworkManager {
    var delegate: YourDelegateProtocol?    
}

获得响应后，从那里将响应发送到您的viewcontroller：

URLSession.shared.dataTask(with: url!) { (data, response, error) in
        if error != nil {
            print(error!)
            onError?(error!)
        } else {
            do {
                let json  = JSON(data: data!)
                  delegate.geDataFromServer(json as String)
                }
                onSuccess?(weather) 
            }
        }
        }.resume()

之后获取viewcontroller中的数据

class WeatherData: UIViewController, YourDelegateProtocol {

   var yourModelClass = YourModelClass() //init model class globally.

   func getDataFromServer(data: String) {
    // populate json String into your model class. Then you are ready to go.
   }
}

Answer 3

您可以在ViewController中创建请求getWeather。此功能使您可以访问Weather对象作为完成处理程序（WeatherCallback =（Weather） - ＆gt; Void）。

Answer 4

在这里，您可以使用Singleton设计模式。创建一个Singleton Weather类，每当您从getWeather函数获得响应时，都会更新您的Weather单例类。当您想要用户响应时，只需从Weather类获取值。

从ViewController调用时，如何检索存储在单独类中的数据？

4 个答案: