ios - JSON 解码器因 URLSession 失败

Question

Swift 的新手，本周尝试学习 SwiftUI。尝试从 Joke API 发出 GET 请求，并最终希望每次按下按钮时都刷新它。

我有一种感觉，我错误地定义了我的结构，或者可能没有正确解码返回的数据。我可以打印数据字符串(作为 json 字典)，但不能通过 Swift 访问值本身。

import SwiftUI

struct Response : Codable {
    var joke: [Joke]
}

struct Joke : Codable {
    var setup: String
    var delivery: String
}

struct ContentView : View {
    @State private var joke = [Joke]()

    func loadData() {
        guard let url = URL(string: "https://sv443.net/jokeapi/v2/joke/Dark?type=twopart") else {
            print("Invalid URL")
            return
        }

        URLSession.shared.dataTask(with: url) { data, res, error in
            if let data = data {
                print("decoding...")
                let str = String(data: data, encoding: .utf8)
                print(str!)

                if let decodedResponse = try? JSONDecoder().decode(Response.self, from: data) {
                    print("decoded!")
                    // cannot get this to print
                    print(decodedResponse.joke)

                    // looks good, let's get out of here
                    return
                }
            }
            print("Fetch failed: \(error?.localizedDescription ?? "Unknown error")")
        }.resume()
    }

    var body : some View {
        Text("test")
        .onAppear(perform: loadData)
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

decoding...
{
    "category": "Dark",
    "type": "twopart",
    "setup": "When I was a kid, I made a really big sandcastle with my grandma.",
    "delivery": "Unfortunately that didn't impress anyone at the cremation...",
    "flags": {
        "nsfw": false,
        "religious": false,
        "political": false,
        "racist": false,
        "sexist": false
    },
    "id": 145,
    "error": false
}
Fetch failed: Unknown error

可能只是我没有发现的愚蠢错误，但希望得到一些解释甚至一些文档。我见过的唯一文档/教程展示了如何使用特定结构化的 JSON 响应。我拉的那个根有一本字典，所以我想这就是差异所在。

我假设我会使用 @escaping 在 UI 中进行渲染？

Answer 1

问题是您正在尝试解码数组:

struct Response : Codable {
    var joke: [Joke]
}

struct Joke : Codable {
    var setup: String
    var delivery: String
}

然而，JSON 响应只是一个对象。

解决方案可能是将其解码为对象而不是数组:

struct Response : Codable {
    var setup: String
    var delivery: String
}

或者，将解码部分更改为解码 Joke :

let decodedResponse = try? JSONDecoder().decode(Joke.self, from: data)