json - 在 SwiftUI 中解码汇率 JSON
问题描述
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()
}
而我的观点:
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。什么会导致这种情况?
它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。
解决方案
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()
}
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