Correct syntax to create progress block before completion handler

Question

I am creating a seperate class to handle my Amazone S3 upload request. However, I am not too sure about the syntax to allow me to create a progress block before completion handler (as shown below in IBAction). Basically what I wish to achieve is inside my VC, I do the following:

@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
        }
    }
}

This is the structure of PostUpload class

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

Change your method to this:

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
        })

    }

Usage:

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

Or:

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