Ios Alamofire:取消（挂起）文件上载

我正在使用Alamofire上传文件，如下所示：

    Alamofire.Manager.upload(
        APIManager.Router.UploadFileRoute,
        multipartFormData : { multipartFormData in
            multipartFormData.appendBodyPart(data: audioData, name: "file", fileName: "file.m4a", mimeType: "audio/m4a")
        }, encodingCompletion: { result in
            switch result {
            case .Success(let request, _, _):
              break
            case .Failure(let encodingError):
              break
            }
    })

一旦此文件开始上载，如何取消（挂起）此文件上载

---

建议对请求对象调用suspend（），但是如何使用上面的文件上载API获得Alamofire.Request对象？此API不返回任何Alamofire.Request对象。

结果表明，只有在编码后请求才准备就绪（请参阅内联注释）

Alamofire.Manager.upload(
    APIManager.Router.UploadFileRoute,
    multipartFormData : { multipartFormData in
        multipartFormData.appendBodyPart(data: audioData, name: "file", fileName: "file.m4a", mimeType: "audio/m4a")
    }, encodingCompletion: { result in
        switch result {
        case .Success(let request, _, _):
          // Reference the request here (will get here immediately)
             request.responseJSON { response in
                  // This closure executes only after request succeeds or fails
             }
          break
        case .Failure(let encodingError):
          break
        }
})