在 SwiftUI 中解码汇率 JSON

Question

我正在尝试解码由 Exchange Rates API 提供的https://api.exchangeratesapi.io/latest。我正在应用我在网上找到的几个教程，但是当我应用自己的详细信息时，出现错误。我的代码如下所示：

struct Response: Codable {
    var results: [Result]
}

struct Result: Codable {
    let base: String
    let date: String
    let rates: [String:Double]
}

检索数据的函数：

func loadData() {
    guard let url = URL(string: "https://api.exchangeratesapi.io/latest") else {
        print("Invalid URL")
        return
    }
    let request = URLRequest(url: url)
    URLSession.shared.dataTask(with: request) { data, response, error in
        if let data = data {
            if let decodedResponse = try? JSONDecoder().decode(Response.self, from: data) {
                // we have good data – go back to the main thread
                DispatchQueue.main.async {
                    // update our UI
                    self.results = decodedResponse.results
                }
                // everything is good, so we can exit
                return
            }
        }
        // if we're still here it means there was a problem
        print("Fetch failed: \(error?.localizedDescription ?? "Unknown error")")
    }.resume()
}

我的看法：

import SwiftUI

struct ExchangeRateTest: View {
    @State private var results = [Result]()

    var body: some View {
                List(results, id: \.base) { item in
            VStack(alignment: .leading) {
                Text(item.base)
            }
        }.onAppear(perform: loadData)
    }
}

我得到的错误是：Fetch Failed: Unknown Error，提示应用程序无法读取在线数据。这是什么原因造成的？

这与我的网络连接无关；如果我应用另一个 JSON，这种方法可以正常工作。

任何帮助将不胜感激。

Answer 1

你可以这样读：

struct RateResult: Codable {
    let rates: [String: Double]
    let base, date: String
}

struct ContentView: View {
    @State private var results = RateResult(rates: [:], base: "", date: "")

    func loadData() {
        guard let url = URL(string: "https://api.exchangeratesapi.io/latest") else {
            print("Invalid URL")
            return
        }
        let request = URLRequest(url: url)
        URLSession.shared.dataTask(with: request) { data, response, error in
            if let data = data {
                if let decodedResponse = try? JSONDecoder().decode(RateResult.self, from: data) {
                    // we have good data – go back to the main thread
                    DispatchQueue.main.async {
                        // update our UI
                        self.results = decodedResponse
                    }
                    // everything is good, so we can exit
                    return
                }
            }
            // if we're still here it means there was a problem
            print("Fetch failed: \(error?.localizedDescription ?? "Unknown error")")
        }.resume()
    }