The object that the receiver (or its parent) makes available to other applications or threads.
- macOS 10.0–10.13Deprecated
The object that the receiver (or its parent) makes available to other applications or threads, or
nil if there is no root object.
To get a proxy to this object in another application or thread, invoke the
root class method with the appropriate arguments.
Changing the root object only affects new connection requests and
root messages to established
NSConnection objects—applications that have proxies to the old root object can still send messages through it.