Sent to the delegate to deliver progress information for a download of a URL asset to a destination file.
- iOS 5.0+
- macOS 10.8+
- UIKit for Mac 13.0+Beta
- tvOS 9.0+
- watchOS 2.0+
The URL connection object downloading the asset.
The number of bytes written since the last call of this method.
The total number of bytes of the downloading asset that have been written to the file.
The total number of bytes of the URL asset once it is completely downloaded and written to a file. This parameter can be zero if the total number of bytes is not known.
This method is invoked repeatedly during the download of a URL asset to the destination file. The delegate typically uses the values of the three “bytes” parameters to update a progress indicator in the application’s user interface.