A handler block used to process operations on a dispatch I/O channel.
- iOS 5.0+
- macOS 10.7+
- Mac Catalyst 13.0+Beta
- tvOS 9.0+
- watchOS 2.0+
The parameters of a dispatch I/O handler are as follows:
done- A flag indicating whether the operation is complete.
data- The data object to be handled. This object is retained by the system for the duration of the handler’s execution and is released when the handler block returns.
error- The error number (if any) reported for the operation. An error number of
0typically indicates the operation was successful.