找不到阿拉莫火缓存

Question

通过执行以下配置，我一直试图设置Alamofire 5.0的缓存：

private func buildURLCache() -> URLCache {
  let capacity = 50 * 1024 * 1024 // MBs
  #if targetEnvironment(macCatalyst)
  return URLCache(memoryCapacity: capacity, diskCapacity: capacity)
  #else
  return URLCache(memoryCapacity: capacity, diskCapacity: capacity, diskPath: nil)
  #endif
}

private func defaultSessionManager(_ requestInterceptor: RequestInterceptor?) -> Alamofire.Session {

  let evaluators: [String: ServerTrustEvaluating] = [
    "google.com": PinnedCertificatesTrustEvaluator(certificates: pinnedCertificates())
  ]

  // Create custom manager
  let configuration = URLSessionConfiguration.af.default
  configuration.headers = HTTPHeaders.default
  configuration.requestCachePolicy = .useProtocolCachePolicy

  URLCache.shared = buildURLCache()
  configuration.urlCache = URLCache.shared

  return Alamofire.Session(
      configuration: configuration,
      interceptor: requestInterceptor,
      serverTrustManager: ServerTrustManager(evaluators: evaluators))
}

函数defaultSessionManager(_)返回一个配置好的Alamofire实例，我将其作为强引用，然后执行如下所示的请求(不要担心，这只是一个示例)：

let alamofireManager = defaultSessionManager(nil)

func getFoos(
  token: String,
  completion: @escaping (Result<[Foo], Error>) -> Void) {

  alamofireManager.request(
    "google.com",
    encoding: JSONEncoding.default,
    headers: headers(token))
    .validate()
    .responseJSON { (dataResponse: AFDataResponse<Any>) in

      if let cacheData = URLCache.shared.cachedResponse(for: dataResponse.request!) {
        print("URLCache.shared Data is from cache")
      } else {
        print("URLCache.shared Data is from Server")
      }

      if let cacheData = URLCache.shared.cachedResponse(for: (dataResponse.request?.urlRequest!)!) {
        print("URLCache.shared urlRequest Data is from cache")
      } else {
        print("URLCache.shared urlRequest Data is from Server")
      }

      //....
    }
}

不幸的是，函数URLCache.shared.cachedResponse正在返回nil，导致函数只打印... Data is from Server。这个应用程序永远不会从缓存中获取数据，知道为什么会发生这种情况吗？

谢谢!

Answer 1

这里有几个问题。

首先，当前response.request返回Alamofire看到的最后一个URLRequest，这不一定是在网络上执行和输出的URLRequest。要查看该值，实际上需要捕获Alamofire Request并检查其task?.currentRequest属性。这将为您提供通过Alamofire和URLSession执行的URLSession。我们也在研究如何使这些URLRequest从响应中获得。

其次，如果您只想检查是否收到缓存的响应，最好检查URLSessionTaskMetrics值，因为这应该提供一个明确的答案，而不需要检查URLCache。

response.metrics?.transactionMetrics.last?.resourceFetchType

如果这个值是.localCache，那么您就知道您的响应来自缓存。