The thread object's dictionary.
- iOS 2.0+
- macOS 10.0+
- tvOS 9.0+
- watchOS 2.0+
You can use the returned dictionary to store thread-specific data. The thread dictionary is not used during any manipulations of the
NSThread object—it is simply a place where you can store any interesting data. For example, Foundation uses it to store the thread’s default
NSAssertion instances. You may define your own keys for the dictionary.