Reads from the file or communications channel in the background and posts a notification when finished.
- iOS 2.0+
- macOS 10.0+
- UIKit for Mac 13.0+Beta
- tvOS 9.0+
- watchOS 2.0+
The runloop modes in which the read completion notification can be posted.
read for details of how this method operates. This method differs from
read in that
modes specifies the run-loop mode (or modes) in which
NSFile can be posted.
You must call this method from a thread that has an active run loop.