URLSession
open override fun URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, didFinishDownloadingToURL: NSURL)
Called when the download finishes successfully. The file is at location — move it to a permanent location in this callback.
open override fun URLSession(session: NSURLSession, task: NSURLSessionTask, didCompleteWithError: NSError?)
Called when the task completes — with or without error. If error is non-null, the download failed.
open override fun URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, didWriteData: Long, totalBytesWritten: Long, totalBytesExpectedToWrite: Long)
Called periodically with download progress.