当文件夹中的文件数为1000时,Dropbox Files.Download不会启动

人气:138 发布:2023-01-03 标签: arrays swift dropbox-api swiftydropbox

问题描述

我在Dropbox论坛上交叉发布了我最初的问题。我认为在这里为快速下载框的用户提供这一功能也是一件好事。

我无法通过wiftyDropbox将整个文件夹下载到本地设备。 我正在执行ListFold和ListFolderContinue(我观察到每个响应将其分块为大约500个文件),并将其附加到本地数组。

之后,我将此数组传递给文件。下载。但是,我发现如果我的文件夹是>;1000个文件(txt文件大小约为0.5-1KB),下载过程将不会开始。

static func downloadMissingFiles(client: DropboxClient, callingProcess: String) {
      let fileManager = FileManager.default
      let localBaseURL = fileManager.urls(for: .cachesDirectory, in: .userDomainMask)[0].appendingPathComponent("Cloud/Dropbox", isDirectory: true)
      
      // Data will be in the form of
      // key   : "/workouts/workout list 1/peye.mrc"
      // value : "//workouts/workout list 1/peye.mrc=_-_=015ca880b135d01000000020cb26de0"
      for dbFiles in Array(dbFileNameRevDict) {
        let dbFilePathLower = dbFiles.key
        let dbFileNameRev = dbFiles.value
        let fullURL = localBaseURL.appendingPathComponent(dbFileNameRev)
        
        if fileManager.fileExists(atPath: fullURL.path) {
          print("  -> FILE EXISTS dbFileNameRev:(dbFileNameRev)")
          localFileList.append(dbFileNameRev)
        } else {
          let destination : (URL, HTTPURLResponse) -> URL = { temporaryURL, response in
            return fullURL
          }
          
          client.files.download(path:dbFilePathLower, overwrite: true, destination: destination)
            .response { response, error in
              if let (_, url) = response {
                print("====> DOWNLOADED:(url.lastPathComponent)")
              } else if let error = error {
               print(error)
            }
            /// This gives a progress of every single file on it's own. Hence, useless
            // .progress { progressData in
            //  print(progressData)
            // }
        }
      }
    }
  }

我已经尝试了各种方法来下载这些文件,我也尝试了一个串行队列来逐个迭代文件数组,但都不起作用。

这就是我在查看hasmore属性时处理ListFold和ListFolderContinue的方式。

      // https://stackoverflow.com/a/52870045/14414215
      if result.hasMore == true {
        processDBMore(client: client, cursor: result.cursor)
      } else {
        // When there is no more files (as indicated by hasMore == false)
        // start downloading the files
        downloadMissingFiles(client: client, callingProcess: "processDBMore-Finish")
        print("PrcessDBMore - dropboxGroup.leave")
        dropboxGroup.leave()
      }

推荐答案

根据Greg(SwiftyDropbox)

每个‘client.files.download’调用通过创建一个文件来下载一个文件 向Dropbox API服务器发出的HTTPS请求。此外,这些呼叫 异步运行,并且在调用完成之前不会阻塞。那 是,调用‘client.files.download’将启动HTTPS请求,但是 将在完成之前返回,并且响应已完全完成 收到了。(一旦请求完成,它只运行提供的块。) 在这种情况下,在您这里展示的代码中,您实际上是 几乎同时启动1000个连接,所以它是 可能会耗尽您的网络连接。您应该更新您的代码 一次只提交其中的一个(或几个)。你提到过你 已尝试使用串行队列,但可能遇到相同的问题, 因为实际请求是异步运行的。

所以我在寻找其他解决方案时,看到了这篇https://stackoverflow.com/a/66227963/14414215,它对我理解信号量是如何工作的,以及实现信号量(除了使用DispatchGroups之外)如何能够正确地控制文件。下载调用有很大帮助。

   static func downloadMissingFiles(client: DropboxClient, callingProcess: String) {
      let fileManager = FileManager.default
      let localBaseURL = fileManager.urls(for: .cachesDirectory, in: .userDomainMask)[0].appendingPathComponent("Cloud/Dropbox", isDirectory: true)
      let semaphore = DispatchSemaphore(value: 1)  // insert desired concurrent downloads value here.

      // Data will be in the form of
      // key   : "/workouts/workout list 1/peye.mrc"
      // value : "//workouts/workout list 1/peye.mrc=_-_=015ca880b135d01000000020cb26de0"
      DispatchQueue.global().async { // Wrap the call within an async block
      for dbFiles in Array(dbFileNameRevDict) {
        semaphore.wait() // Decrement the semaphore counter
        let dbFilePathLower = dbFiles.key
        let dbFileNameRev = dbFiles.value
        let fullURL = localBaseURL.appendingPathComponent(dbFileNameRev)
        
        if fileManager.fileExists(atPath: fullURL.path) {
          print("  -> FILE EXISTS dbFileNameRev:(dbFileNameRev)")
          localFileList.append(dbFileNameRev)
          semaphore.signal()  // Increment semaphore counter
        } else {
          let destination : (URL, HTTPURLResponse) -> URL = { temporaryURL, response in
            return fullURL
          }
          
          client.files.download(path:dbFilePathLower, overwrite: true, destination: destination)
            .response { response, error in
              if let (_, url) = response {
                print("====> DOWNLOADED:(url.lastPathComponent)")
                // we've reached here means we've successfully download the file
                // So we can (release)increment semaphore counter
                semaphore.signal() 
              } else if let error = error {
               print(error)
            }
            /// This gives a progress of every single file on it's own. Hence, useless
            // .progress { progressData in
            //  print(progressData)
            // }
        }
      }
    }
   }
  }

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