Swift 通用 Json 解析器

Question

我有一个通用的 JSON 解析器，可以解码数组

class JSONParserFromStruct {
    typealias result<T> = (Result<[T], Error>) -> Void

    func downloadList<T: Decodable>(of _: T.Type,
                                    from data: Data,
                                    completion: @escaping result<T>) {
        do {
            let decodedData: [T] = try! JSONDecoder().decode([T].self, from: data)
            completion(.success(decodedData))
        } catch {
            completion(.failure(DataError.decodingError))
        }
    }
}

捆绑包中的 Users.json 文件

{
    "name": "Taylor Swift"
}

像这样调用它：

func performRequest() {
    let url = Bundle.main.url(forResource: "Users", withExtension: "json")!
    let data = try! Data(contentsOf: url)
    genericParser.downloadList(of: User.self, from: data) { result in
        switch result {
        case let .failure(error):
            if error is DataError {
                print("eroarea este: \(error.localizedDescription)")

                print(url)

            } else {
                print("err is \(error.localizedDescription)")
            }
            print(error.localizedDescription)

        case let .success(weather):
            print(weather)
        }
    }
}

奇迹般有效

但是，当尝试使用名为 Weather.json 的不同 json 文件时，它会失败并显示错误

“debugDescription：“预期解码数组，但找到了字典”

这是我收到错误的 json

{
    "main": {
        "temp": 281.52,
        "feels_like": 278.99,
        "temp_min": 280.15,
        "temp_max": 283.71,
        "pressure": 1016,
        "humidity": 93
    }
}

数据模型

struct Weather: Codable {
    let main: Main
}

struct Main: Codable {
    let temp: Double
}

...使用相同的 JSONParserFromStruct 类，但是失败了。

这就是它的名字

 func performRequest() {
    let url = Bundle.main.url(forResource: "Weather", withExtension: "json")!
    let data = try! Data(contentsOf: url)
    genericParser.downloadList(of: Weather.self, from: data) { result in
        switch result {
        case let .failure(error):
            if error is DataError {
                print("eroarea este: \(error.localizedDescription)")

                print(url)

            } else {
                print("err is \(error.localizedDescription)")
            }
            print(error.localizedDescription)

        case let .success(weather):
            print(weather)
        }
    }
}

Answer 1

您的解析器不够通用，因为它只能解码数组。

泛型类型 T 可以是任何东西，单个对象也可以是数组，所以只需使用T

class JSONParserFromStruct {
    typealias ResultBlock<T> = (Result <T, Error>) -> Void

    func downloadList<T: Decodable>(of type: T.Type,
                                      from data: Data,
                                      completion: @escaping ResultBlock<T>) {

        do {
            let decodedData: T = try JSONDecoder().decode(T.self, from: data)
            completion(.success(decodedData))
        }
        catch {
            completion(.failure(DataError.decodingError))
        }
    }
}

要解码数组，User请将数组指定为参数类型

genericParser.downloadList(of: [User].self, from: data)

现在

genericParser.downloadList(of: Weather.self, from: data)

应该可以工作