设计网络层

问题

如何设计一个可扩展的 iOS 网络层？

答案

分层架构

API 协议定义

protocol APIEndpoint {
    associatedtype Response: Decodable
    var path: String { get }
    var method: HTTPMethod { get }
    var headers: [String: String]? { get }
    var body: Encodable? { get }
}

struct GetUserEndpoint: APIEndpoint {
    typealias Response = User
    let userId: String
    var path: String { "/api/users/\(userId)" }
    var method: HTTPMethod { .get }
    var headers: [String: String]? { nil }
    var body: Encodable? { nil }
}

网络客户端

class NetworkClient {
    private let session: URLSession
    private let baseURL: URL
    private var interceptors: [RequestInterceptor] = []

    func request<E: APIEndpoint>(_ endpoint: E) async throws -> E.Response {
        var request = buildURLRequest(endpoint)

        // 拦截器链 - 请求前
        for interceptor in interceptors {
            request = try await interceptor.intercept(request: request)
        }

        let (data, response) = try await session.data(for: request)

        guard let httpResponse = response as? HTTPURLResponse,
              200..<300 ~= httpResponse.statusCode else {
            throw NetworkError.serverError(statusCode: (response as? HTTPURLResponse)?.statusCode ?? 0)
        }

        return try JSONDecoder().decode(E.Response.self, from: data)
    }
}

// 拦截器
protocol RequestInterceptor {
    func intercept(request: URLRequest) async throws -> URLRequest
}

struct AuthInterceptor: RequestInterceptor {
    func intercept(request: URLRequest) async throws -> URLRequest {
        var request = request
        request.setValue("Bearer \(token)", forHTTPHeaderField: "Authorization")
        return request
    }
}

关键设计点

设计点	方案
类型安全	泛型 + Codable
可扩展	拦截器链模式
重试	自动重试 + 指数退避
Mock	协议抽象，注入 MockSession

---

常见面试问题

Q1: Token 过期如何自动刷新？

答案：在拦截器中检测 401 响应 → 刷新 Token → 重新发起请求。需要加锁避免多个请求并发刷新。

相关链接

• Moya