解析json数据后更新swiftui文本视图

Posted 2023-02-23

【中文标题】解析json数据后更新swiftui文本视图

【英文标题】：Updating swiftui text view after parsing json data

【发布时间】：2019-12-30 02:09:00

【问题描述】：

我有一个函数可以发送到 api 并获取股票价格。我有一个返回双精度的函数，当我运行代码时，我可以看到正确的价格打印到控制台。当我尝试将该价格设置为函数内的变量以便函数可以返回它时，我在文本视图中只得到 0.000。有人可以告诉我我做错了什么吗？我的代码如下。

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
       

【参考方案1】：

您可以通过更改 @State 变量来更新您的 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