在完成处理程序之前创建进度块的正确语法

Question

我正在创建一个独立的类来处理我的Amazone S3上传请求。但是，我不太确定语法是否允许我在完成处理程序之前创建进度块（如下面的IBAction所示）。基本上我想达到的就是我的VC里面，我做了以下内容：

@IBAction startUpload() { 
    let uploadPost = PostUpload(imageNSData: someNSData)() 

    uploadPost.uploadBegin { 
     // Some block here to grab the "progress_in_percentage" variable so I can use it on progress bar 
     { 
      // Some completion block when the request is completed and check if any error was returned 
     } 
    } 
} 

这是PostUpload类

class PostUpload { 

    var imageNSData: NSData! 

    init(imageNSData: NSData) { 
     self.imageNSData = imageNSData 
    } 

    func uploadBegin(completion:(success: Bool, error: NSError?) -> Void) { 

     // 1. Create upload request 
     let uploadRequest = AWSS3TransferManagerUploadRequest(


     // Track progress through an AWSNetworkingUploadProgressBlock 
     uploadRequest?.uploadProgress = {[weak self](bytesSent:Int64, totalBytesSent:Int64, totalBytesExpectedToSend:Int64) in 
      dispatch_sync(dispatch_get_main_queue(), {() -> Void in 

       let progress_in_percentage = Float(totalBytesSent)/Float(totalBytesExpectedToSend) 
       print(progress_in_percentage) 
      }) 
     } 

     // 3. Upload to Amazone S3 
     let transferManager = AWSS3TransferManager.defaultS3TransferManager() 
     transferManager.upload(uploadRequest).continueWithExecutor(AWSExecutor.mainThreadExecutor(), withBlock: { (task: AWSTask) -> AnyObject? in 

      if let error = task.error { 
       completion(true, error) 

      } else { 
       completion(true, nil) 
      } 
      return nil 
     }) 

    } 
} 

Answer 1

你的方法改成这样：

func uploadBegin(progressUpdate: ((percent: Float) -> Void)? = nil, completion:(success: Bool, error: NSError?) -> Void) { 

     // 1. Create upload request 
     let uploadRequest = AWSS3TransferManagerUploadRequest(


      // Track progress through an AWSNetworkingUploadProgressBlock 
      uploadRequest?.uploadProgress = {[weak self](bytesSent:Int64, totalBytesSent:Int64, totalBytesExpectedToSend:Int64) in 
       dispatch_sync(dispatch_get_main_queue(), {() -> Void in 

        let progress_in_percentage = Float(totalBytesSent)/Float(totalBytesExpectedToSend) 
        print(progress_in_percentage) 

        //Call this to update progress 
        progressUpdate?(progress_in_percentage) 
       }) 
     } 

     // 3. Upload to Amazone S3 
     let transferManager = AWSS3TransferManager.defaultS3TransferManager() 
     transferManager.upload(uploadRequest).continueWithExecutor(AWSExecutor.mainThreadExecutor(), withBlock: { (task: AWSTask) -> AnyObject? in 

      if let error = task.error { 
       completion(true, error) 

      } else { 
       completion(true, nil) 
      } 
      return nil 
     }) 

    } 

用法：

uploadBegin { (success, error) in 
      //completion block 
     } 

或者：

uploadBegin({ (percent) in 
    //Update Progress on UI 
    }) { (success, error) in 
     //completion block 
} 

Answer 2

可以在功能参数中添加多个闭合，在结构中的情况下，只需添加进度回调封口的功能，第一个参数

func uploadBegin(uploadProgress:(percentage: Float) -> Void, completion:(success: Bool, error: NSError?) -> Void) { 

    // 1. Create upload request 
    let uploadRequest = AWSS3TransferManagerUploadRequest(

     // Track progress through an AWSNetworkingUploadProgressBlock 
     uploadRequest?.uploadProgress = {[weak self](bytesSent:Int64, totalBytesSent:Int64, totalBytesExpectedToSend:Int64) in 
      dispatch_sync(dispatch_get_main_queue(), {() -> Void in 

       let progress_in_percentage = Float(totalBytesSent)/Float(totalBytesExpectedToSend) 
       // report progress here 
       uploadProgress(percentage: progress_in_percentage) 
       print(progress_in_percentage) 
      }) 
    } 

    // 3. Upload to Amazone S3 
    let transferManager = AWSS3TransferManager.defaultS3TransferManager() 
    transferManager.upload(uploadRequest).continueWithExecutor(AWSExecutor.mainThreadExecutor(), withBlock: { (task: AWSTask) -> AnyObject? in 

     if let error = task.error { 
      completion(true, error) 

     } else { 
      completion(true, nil) 
     } 
     return nil 
    }) 

} 

使用

uploadPost.uploadBegin({ (percentage) in 
    // progress handle here 
}) { (success, error) in 
    // completion block 
}