结合处理不同类型的发布者

Question

我真的是Combine 的新手，我一直被这个问题困扰。我有基本的注册表单，如果一切正常，返回空响应，返回 200 代码；如果表单有一些注册失败，返回 442。

这是可以处理空响应并且工作正常的代码

extension Route where ResultType: EmptyResult {
    func emptyResult() -> AnyPublisher<Void, APIError> {
        return URLSession.shared.dataTaskPublisher(for: urlRequest)
            .print("EMPTY RESULT")
            .tryMap { data, response in
                guard let httpResponse = response as? HTTPURLResponse else { throw APIError.nonHttpResponse(description: "Not http resp") }
                let statusCode = httpResponse.statusCode
                
                guard (200..<300).contains(statusCode) else { throw APIError.nonHttpResponse(description: "bad response")
                }
                    return Void()
            }.mapError { error in
                print("Error \(error)")
                return .network(description: error.localizedDescription)
            }
            .eraseToAnyPublisher()
    }
}

但是，我如何返回其他类型的发布者？例如

struct CustomError: Decodable {
    let usernameError: String
    let emailError: String
}

我的网络通话：

    API.registration(name: name, email: email, password: password, schoolID: selectedSchool?.id ?? 0)
        .print("Registration")
        .receive(on: DispatchQueue.main)
        .sink(receiveCompletion: { (completion) in
            switch completion {
            case let .failure(error):
                print("ERROR \(error)")
            case .finished: break
            }
        }, receiveValue: { value in
            print(value)
        })
        .store(in: &disposables)

Answer 1

所以你有一个网络请求，如果请求成功，它会返回一个 200 响应和一个空正文，而如果是表单错误，它会返回一个特定的状态码和响应中的错误。

我建议将Publisher 的Output 类型保留为Void，但是，如果出现表单错误，请解码错误并将其作为APIError 的一部分抛出。

struct LoginError: Decodable {
    let usernameError: String
    let emailError: String
}

enum APIError: Error {
    case failureStatus(code: Int)
    case login(LoginError)
    case nonHttpResponse(description: String)
    case network(Error)
}

func emptyResult() -> AnyPublisher<Void, APIError> {
    return URLSession.shared.dataTaskPublisher(for: urlRequest)
        .print("EMPTY RESULT")
        .tryMap { data, response in
            guard let httpResponse = response as? HTTPURLResponse else { throw APIError.nonHttpResponse(description: "Not http response") }
            let statusCode = httpResponse.statusCode

            guard (200..<300).contains(statusCode) else {
                if statusCode == 442 {
                    let loginError = try JSONDecoder().decode(LoginError.self, from: data)
                    throw APIError.login(loginError)
                } else {
                    throw APIError.failureStatus(code: statusCode)
                }
            }
            return Void()
        }.mapError { error in
            switch error {
            case let apiError as APIError:
                return apiError
            default:
                return .network(error)
        }
    }
        .eraseToAnyPublisher()
}

然后您可以通过switching 处理error in sink 中的特定错误：

API.registration(name: name, email: email, password: password, schoolID: selectedSchool?.id ?? 0)
    .print("Registration")
    .receive(on: DispatchQueue.main)
    .sink(receiveCompletion: { (completion) in
        switch completion {
        case let .failure(error):
            switch error {
            case .login(let loginError):
                print("Login failed, \(loginError.emailError), \(loginError.usernameError)")
            default:
                print(error)
            }
        case .finished: break
        }
    }, receiveValue: { value in
        print(value)
    })
    .store(in: &disposables)