承诺使用Typescript重试成功/失败 [英] Promise retries until success/failure with Typescript

问题描述

我的移动应用程序连续将多个文件上传到服务器，通常来自连接强度可疑的偏远地区。出于这个原因，我想尝试发送文件。我还希望继续并在发生故障时尝试下一个，并在导出结束时显示所有错误消息（即上传10个文件，3个失败......）

My mobile app uploads several files to the server in succession, often from remote areas with questionable connection strength. For this reason, I want to make a few attempts to send the file. I also want to move on and attempt the next one in the event of a failure, with all error messages displayed at the end of the export (ie "10 files uploaded, 3 failed...")

然而，我无法通过promises找出递归重试模式。这是我到目前为止所拥有的：

However, I'm having trouble figuring out the recursive retry pattern with promises. Here's what I have so far:

sendFile(params, retries = 3){
    console.log("SENDING FILE: ", retries, "attempts remaining", params)

    return new Promise((resolve, reject)=>{
      if(retries > 0){
        this._sendFile(params)
        .then(()=>{
          // Upload Success
          console.log("Upload Success!")
          resolve()
        })
        .catch((err)=>{
          console.log("Upload Fail", err)
          // Retry
          this.sendFile(params, --retries)
        })
      }else{
        console.log("Failed 3 times!!!")
        //Record error
        this.exportStatus.errors.push({
          message:"A file failed to upload after 3 attempts.",
          params: params
        })

        //Resolve and move on to next export
        resolve()

      }
    })

  }

  _sendFile(params){

      // Mobile - File Transfer

        let options = {
          fileKey: "file_transfer",
          fileName: params.fileName,
          httpMethod: "PUT",
          chunkedMode: false,
          headers: {
            "x-user-email":this.settings.user.email,
            "x-user-token":this.settings.user.authentication_token,
          }
        }

        let fileTransfer = this.transfer.create()
        let url = encodeURI(this.settings.api_endpoint + params.url)

        return fileTransfer.upload(params.file, url, options, true)


  }

当我在服务器上引发异常时，我会看到失败3次!!!错误消息，但调用的承诺不会解析导出的其余部分继续。我相信这是因为我创建了嵌套的promises（即每次重试都会创建一个新的promise）。如何在3次重试后解除原始承诺？

When I raise an exception on the server, I'll see the "Failed 3 times!!!" error message, but the calling promise does not resolve for the rest of the export to move on. I believe this is because I'm created nested promises (ie creating a new promise with each retry). How can I have the original promise resolve after 3 retries?

谢谢！

推荐答案

以下是最终的工作：

  sendFile(params, retries = 3, promise = null){
    console.log("SENDING FILE: ", retries, "attempts remaining", params)

    if(retries > 0){
      return this._sendFile(params)
      .then(()=>{
        // Upload Success
        console.log("Upload Success!")
        return Promise.resolve(true)
      })
      .catch((err)=>{
        console.log("Upload Fail", err)

        this.exportStatus.retries++

        return this.sendFile(params, --retries) // <-- The important part
      })
    }else{
      console.log("Failed 3 times!!!")

      this.exportStatus.errors.push({
        message:"A file failed to upload after 3 attempts.",
        params: params
      })

      return Promise.resolve(false)

    }

  }

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