Tells the delegate that the download task has resumed downloading.
- iOS 7.0+
- macOS 10.9+
- tvOS 9.0+
- watchOS 2.0+
The session containing the download task that finished.
The download task that resumed. See explanation in the discussion.
If the file's cache policy or last modified date prevents reuse of the existing content, then this value is zero. Otherwise, this value is an integer representing the number of bytes on disk that do not need to be retrieved again.
The expected length of the file, as provided by the
Content-Lengthheader. If this header was not provided, the value is
Transfer Size Unknown
If a resumable download task is canceled or fails, you can request a
resume object that provides enough information to restart the download in the future. Later, you can call
download with that data.
When you call those methods, you get a new download task. As soon as you resume that task, the session calls its delegate’s
URLSession: method with that new task to indicate that the download is resumed.