解析json数据后更新swiftui文本视图

Question

我有一个可以访问api并获取股票价格的函数。我有返回双精度值的函数，运行代码时可以看到正确的价格打印到控制台。当我尝试将价格设置为函数内部的变量以便函数可以返回价格时，我在文本视图中仅获得0.000。有人可以告诉我我在做什么错吗？我的代码在下面。

import SwiftUI

struct ListView: View {

    var body: some View {


        List {


            HStack {
                Text("Stock Price (15 Min. delay)")
                Spacer()
                Text("\(getStockPrice(stock: symbol))")
            }



        }
    }

    func getStockPrice(stock: String) -> Double {

           var thePrice = Double()

           guard let url = URL(string: "my url to get data") else {

               fatalError("URL does not work!")

           }
           URLSession.shared.dataTask(with: url) { jsonData, _, _ in

               guard let jData = jsonData else {return}

               do {
                   if let json = try JSONSerialization.jsonObject(with: jData, options: []) as? [String: Any] {

                        if let pricer = json["latestPrice"] as? Double {

                                print(pricer)

                                thePrice = pricer


                        }



                   }
               } catch let err {
                   print(err.localizedDescription)
               }



           }.resume()
        return thePrice
       }

}

Answer 1

您可以通过更改@State变量来更新UI，如下面的代码所示：

struct UpdatingPriceAsync: View {

    @State var stockPrice: Double = 0.0

    var body: some View {


        List {

            HStack {
                Text("Stock Price (15 Min. delay)")
                Spacer()
                Text("\(stockPrice)")
                    .onAppear() {
                        self.updateStockPrice(stock: "something")
                }
            }

        }

    }

    private func updateStockPrice(stock: String) {

        DispatchQueue.main.asyncAfter(deadline: .now() + 1) { // sort of URL session task
            DispatchQueue.main.async { // you need to update it in main thread!
                self.stockPrice = 99.9
            }
        }

    }

}