我很難將下載的json回應放入我的資料模型并在代碼中訪問它

我有以下代碼，我試圖在其中將匯率下載到我的應用程式中以用于貨幣轉換。資料獲取似乎作業正常，json 解碼模型也是如此，但我無法通過 Rates 變數獲取資料

import SwiftUI
struct ExchangeRates: Codable {
    var conversionRates: [String: Double]?
    
    init(conversionRates:[String:Double]) {
        
        self.conversionRates = conversionRates
    }
    enum CodingKeys: String, CodingKey {
        case conversionRates = "conversion_rates"
    }
}

class DownloadingData:ObservableObject{
    
    @Published var Rates:ExchangeRates = ExchangeRates.init(conversionRates: ["test" : 0])
    
    init() {
        datatask()
    }
    
    func datatask() {
        guard let url = URL(string: "https://v6.exchangerate-api.com/v6/********************/latest/GBP") else {return}
        URLSession.shared.dataTask(with: url){(data,response,error) in
            
            guard let data = data else {
                print("no data")
                return
            }
            guard error == nil else {
                print("error :\(String(describing: error))")
                return
            }
            guard let response = response as? HTTPURLResponse else {
                print("invalid response")
                return
            }
            guard response.statusCode >= 200 && response.statusCode < 300 else {
                print("status code should be 2xx, but is \(response.statusCode)")
                return
            }
            guard let rates = try? JSONDecoder().decode(ExchangeRates.self, from: data) else {return}
            print(rates) **// this works and prints out data**
            DispatchQueue.main.async {
                [weak self] in
                self?.Rates = rates
                print(self?.Rates) **// this works and prints out the data**
            }
            print(self.Rates) **// this doesnt print out anything**
        }.resume()
        print(Rates) **// this doesnt print out anything**
    }
}

我似乎無法將資料輸入到 Rates Variable 中，請提供任何指導

謝謝

這是控制臺輸出的示例：

ExchangeRates(conversionRates: Optional(["test": 0.0])) Optional(test3.ExchangeRates(conversionRates: Optional(["BZD": 2.7002, "PHP": 68.7948, "PGK": 4.725, "BND": 1.8176) “HNL”：32.8885、“TND”：3.7553、“BDT”：115.2218、“SBD”：10.6866、“NIO”：47.4824、“XDR”：0.963、“IDR”：19213、“XCD6”：19213.906 ": 1.7152, "UGX": 4778.6135,])

uj5u.com熱心網友回復：

宣告rates - 請以小寫字母開頭 - 作為空字典

@Published var rates = [String:Double]()

在 struct 中洗掉 init 方法并宣告字典也是非可選的

struct ExchangeRates: Decodable {
    let conversionRates: [String: Double]
    
    enum CodingKeys: String, CodingKey {
        case conversionRates = "conversion_rates"
    }
}

在DispatchQueue閉包中賦值conversionRates給rates

DispatchQueue.main.async { // no weak self needed
    self.rates = rates.conversionRates
}

在視圖中列舉字典 rates

uj5u.com熱心網友回復：

你可以試試這個，使用你的ExchangeRates結構：

class DownloadingData: ObservableObject{
    @Published var rates = ExchangeRates(conversionRates: ["test" : 0])
    
    init() {
        datatask()
    }
    
    func datatask() {
        guard let url = URL(string: "https://v6.exchangerate-api.com/v6/********************/latest/GBP") else {return}
        URLSession.shared.dataTask(with: url){(data,response,error) in
            
            guard let data = data else {
                print("no data")
                return
            }
            guard error == nil else {
                print("error :\(error)")
                return
            }
            guard let response = response as? HTTPURLResponse else {
                print("invalid response")
                return
            }
            guard response.statusCode >= 200 && response.statusCode < 300 else {
                print("status code should be 2xx, but is \(response.statusCode)")
                return
            }
            guard let exRates = try? JSONDecoder().decode(ExchangeRates.self, from: data) else {return}
            print(exRates)
            DispatchQueue.main.async {
                self.rates = exRates   // <--- here
                print(self.rates)     // <--- here
            }
            // print(self.rates) // <--- NEVER here
        }.resume()
    }
}

               

EDIT-1：完成關閉：

class DownloadingData: ObservableObject{
    @Published var rates = ExchangeRates(conversionRates: ["test" : 0])
    
    init() {
        datatask() { isDone in
            print(self.rates) // <--- here OK
        }
    }
    
    func datatask(completion: @escaping(Bool) -> ()) {   // <--- here 
        guard let url = URL(string: "https://v6.exchangerate-api.com/v6/********************/latest/GBP") else {return}
        URLSession.shared.dataTask(with: url){(data,response,error) in
            
            guard let data = data else {
                print("no data")
                return
            }
            guard error == nil else {
                print("error :\(error)")
                return
            }
            guard let response = response as? HTTPURLResponse else {
                print("invalid response")
                return
            }
            guard response.statusCode >= 200 && response.statusCode < 300 else {
                print("status code should be 2xx, but is \(response.statusCode)")
                return
            }
            guard let exRates = try? JSONDecoder().decode(ExchangeRates.self, from: data) else {return}
            print(exRates)   // <--- here OK
            DispatchQueue.main.async {
                self.rates = exRates
                print(self.rates)     // <--- here OK
                completion(true)      // <--- here return completion
            }
        }.resume()
    }
}

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