Is it possible to use URL session delegate method for progress and completion handler for completion? Or better option?

Question

I'm using my downloader class to download files through URLSession delegate method and updating progress bar with progress from the delegate method. I call the download class like this from my View:

downloader.download(url: self.video.url, fileName: self.video.filePath)

After this is complete I want to update some variables in my View to stop showing the progress bar. I was thinking of using a completion handler but I don't think this would really work whilst using the delegate for progress and completion. And I can't access the variables of my view to update in the completion delegate method of downloader.

I was wondering if it would be possible to use the delegate method for progress updates and a completion handler for completion? Is this possible?

Do you have any ideas how I could do it?

Here is my downloader class:

class download: NSObject, URLSessionDelegate, URLSessionDownloadDelegate{

    @ObservedObject var globalScrollTitle: ScrollTitle = ScrollTitle.sharedInstance

    func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didWriteData bytesWritten: Int64, totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64){

        let progress = Float(totalBytesWritten) / Float(totalBytesExpectedToWrite)
        DispatchQueue.main.async(execute: {
            self.globalScrollTitle.mainprogress = CGFloat(progress)
            print(self.globalScrollTitle.mainprogress)
        })
    }

    func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL) {
        // check for and handle errors:
        // * downloadTask.response should be an HTTPURLResponse with statusCode in 200..<299
        print("download complete!")

        do{
            let downloadedData = try Data(contentsOf: location)

            DispatchQueue.main.async(execute: {
                print("transfer completion OK!")

                let documentDirectoryPath = NSSearchPathForDirectoriesInDomains(.downloadsDirectory, .userDomainMask, true).first! as NSString
                let destinationPath = documentDirectoryPath.appendingPathComponent((downloadTask.response?.suggestedFilename)!)

                let pdfFileURL = URL(fileURLWithPath: destinationPath)
                FileManager.default.createFile(atPath: pdfFileURL.path,
                                               contents: downloadedData,
                                               attributes: nil)

                if FileManager.default.fileExists(atPath: pdfFileURL.path) {
                    print("file present!") // Confirm that the file is here!
                }
            })
        } catch {
            print (error.localizedDescription)
        }


    }

    func download(url: String, fileName: String) {
        let myUrl = URL(string: url)
        let request = URLRequest(url:myUrl!)
        //let config = URLSessionConfiguration.default
        //let operationQueue = OperationQueue()
        let session = URLSession(configuration: .default, delegate: self, delegateQueue: nil)
        let downloadTask = session.downloadTask(with: request)
        downloadTask.resume()
        //completion()
    }
}

Answer 1

Thanks to Faysal Ahmed, I managed to find the following solution that worked. This allowed me to track my progress to update UI whilst also using a completion handler.

    observation = task.progress.observe(\.fractionCompleted) { progress, _ in
        DispatchQueue.main.async(execute: {
            self.globalScrollTitle.mainprogress = CGFloat(progress.fractionCompleted)
        })
        if progress.fractionCompleted == 1 {
            completion()
        }
    }

My download func now looks like this:

func download(url: String, fileName: String, completion: @escaping () -> Void) {
        let myUrl = URL(string: url)
        let request = URLRequest(url:myUrl!)
        let config = URLSessionConfiguration.default
        let operationQueue = OperationQueue()
        let session = URLSession(configuration: config, delegate: nil, delegateQueue: operationQueue)

        let task = session.dataTask(with: request) { (data, response, error) in
            guard error == nil else {
                print(error!)
                return
            }
            // Success
            if let statusCode = (response as? HTTPURLResponse)?.statusCode {
                print("Success: \(statusCode)")
            }

            do {
                let documentFolderURL = try FileManager.default.url(for: .downloadsDirectory, in: .userDomainMask, appropriateFor: nil, create: false)
                let fileURL = documentFolderURL.appendingPathComponent(fileName)
                try data!.write(to: fileURL)

                DispatchQueue.main.async {

                    if FileManager.default.fileExists(atPath: fileURL.path) {
                        print("file present!") // Confirm that the file is here!
                    }
                }

            } catch  {
                print("error writing file \(error)")
            }
        }

        observation = task.progress.observe(\.fractionCompleted) { progress, _ in
            DispatchQueue.main.async(execute: {
                self.globalScrollTitle.mainprogress = CGFloat(progress.fractionCompleted)
            })
            if progress.fractionCompleted == 1 {
                completion()
            }
        }

        task.resume()
    }
}