Question

我正在尝试解码以下json：

    [
        {
            "breeds":[
            {
            "weight":{
            "imperial":"65 - 75",
            "metric":"29 - 34"
            },
            "height":{
            "imperial":"21 - 28",
            "metric":"53 - 71"
            },
            "id":14,
            "name":"American Foxhound",
            "country_code":"US",
            "bred_for":"Fox hunting, scent hound",
            "breed_group":"Hound",
            "life_span":"8 - 15 years",
            "temperament":"Kind, Sweet-Tempered, Loyal, Independent, Intelligent, Loving"
            }
            ],
            "id":"p4xvDeEpW",
            "url":"https://cdn2.thedogapi.com/images/p4xvDeEpW.jpg",
            "width":680,
            "height":453
        }
    ]

我的模型设置为：

struct Request: Decodable {
    let response: [Response]
}

struct Response: Decodable {
    let breeds: [Dog]
    let url: String
}

struct Dog: Decodable {
    let weight: Measurement
    let height: Measurement
    let name: String
    let countryCode: String?
    let breedGroup: String
    let lifeSpan: String
    let temperament: String
    let origin: String?
}

struct Measurement: Decodable {
    let imperial: String
    let metric: String
}

我按如下方式调用API：

func fetchDogs(with request: URLRequest, completion: @escaping (([Dog]?, String?, Error?) -> ())) {
    URLSession.shared.dataTask(with: request) { (data, response, error) in
        let decoder = JSONDecoder()
        decoder.keyDecodingStrategy = .convertFromSnakeCase

        guard let data = data,
            let request = try? decoder.decode(Request.self, from: data) else {
                completion(nil, nil, error)
                return
        }

        completion(request.response[0].breeds, request.response[0].url, nil)
        }.resume()
}

但是它总是命中警戒completion(nil, nil, error)行，我不确定为什么我不确定如何将JSON的前几行分开。使用：

struct Request: Decodable {
    let response: [Response]
}

似乎不正确。如果我更新了对Response结构进行解码的请求，它仍然会引起警惕。

我的请求构建器如下：

struct RequestBuilder {
    private let baseURLString: String

    static var defaultBuilder: RequestBuilder {
        return RequestBuilder(
            baseURLString: Constant.URL.dogsBase
        )
    }

    func dogsRequest() -> URLRequest {
        return dogRequest(path: Constant.Path.search)
    }

    private func dogRequest(path: String) -> URLRequest {
        guard var components = URLComponents(string: baseURLString) else {
            preconditionFailure(Constant.PreconditionFailure.baseURL)
        }

        components.path = path

        guard let url = components.url else {
            preconditionFailure(Constant.PreconditionFailure.baseURL)
        }
        var request = URLRequest(url: url)
        request.setValue(Constant.Key.dogs, forHTTPHeaderField: "x-api-key")

        return request
    }
}

可以找到here

Answer 1

问题在于，当您将Request.self传递给decode.decode时，JSONDecoder期望找到一个Dictionary，其密钥为response，这是由于您声明了{ {1}}。

您只需要将Request传递给[Response].self方法。

decode

如果您没有使用guard let data = data, let request = try? decoder.decode([Response].self, from: data) else { completion(nil, nil, error) return }掩盖解码错误，则会从错误消息中立即看到问题：

typeMismatch（Swift.Dictionary，Swift.DecodingError.Context（codingPath：[]，debugDescription：“预期用于解码Dictionary，但找到一个数组。”，底层错误：无））

在不确定代码是否可以正常工作时，应该始终在try?块中使用普通的try语句，因为这样实际上可以看到错误消息。 do-catch会引发非常有用的错误，因此建议您不要使用JSONDecoder将它们掩盖到nil中。

解码Json无法正常工作，也不给出错误

1 个答案: