使用具有 API 响应的泛型 / Codable 204 NO CONTENT

Question

我正在使用泛型和可编码的URLSession.

当我收到来自 API 的响应时，我检查状态是否在 200 - 299 范围内并像这样解码数据

        guard let data = data, let value = try? JSONDecoder().decode(T.self, from: data) else {
            return completion(.error("Could not decode JSON response"))
        }
        completion(.success(value)) 

然后将其传递给完成处理程序，一切正常。

我有一个新的端点，我也必须 POST，但是，这个端点返回一个没有内容正文的 204。

因此，我无法解码响应，只是因为我无法传入类型？

我的完成处理程序期望

enum Either<T> {
    case success(T)
    case error(String?)
}

并像这样打开我的响应状态代码

   case 204:
        let value = String(stringLiteral: "no content")
        return completion(.success(value))

产生错误

“Either< > ”中的成员“success”产生“Either”类型的结果，但上下文需要“Either< >”

我的 APIClient 是

protocol APIClientProtocol: class {
    var task: URLSessionDataTask { get set }
    var session: SessionProtocol { get }
    func call<T: Codable>(with request: URLRequest, completion: @escaping (Either<T>) -> Void) -> Void
    func requestRefreshToken<T: Codable>(forRequest failedRequest: URLRequest, completion: @escaping (Either<T>) -> Void) -> Void
}

extension APIClientProtocol {
    func call<T: Codable>(with request: URLRequest, completion: @escaping (Either<T>) -> Void) -> Void {
        task = session.dataTask(with: request, completionHandler: { [weak self] data, response, error in
            guard error == nil else {
                return completion(.error("An unknown error occured with the remote service"))
            }
            guard let response = response as? HTTPURLResponse else {
                return completion(.error("Invalid HTTPURLResponse recieved"))
            }

            switch response.statusCode {
            case 100...299:
                guard let data = data else { return completion(.error("No data in response")) }
                guard let value = try? JSONDecoder().decode(T.self, from: data) else { return completion(.error("Could not decode the JSON response")) }
                completion(.success(value))
            case 300...399: return completion(.error(HTTPResponseStatus.redirection.rawValue))
            case 400: return completion(.error(HTTPResponseStatus.clientError.rawValue))
            case 401: self?.requestRefreshToken(forRequest: request, completion: completion)
            case 402...499: return completion(.error(HTTPResponseStatus.clientError.rawValue))
            case 500...599: return completion(.error(HTTPResponseStatus.serverError.rawValue))
            default:
                return completion(.error("Request failed with a status code of \(response.statusCode)"))
            }
        })
        task.resume()
    }
}

Answer 1

使您的Either枚举成功类型可选

enum Either<T> {
    case success(T?)
    case error(String)
}

创建响应状态的案例204，传递 nil

    case 204:
        completion(.success(nil))

然后你可以使用 atypealias并创建一些通用的东西，比如

typealias NoContentResponse = Either<Bool>

然后您应该能够打开NoContentResponse。