Returns the current thread’s priority.
- iOS 2.0+
- macOS 10.2+
- tvOS 9.0+
- watchOS 2.0+
The current thread’s priority, which is specified by a floating point number from 0.0 to 1.0, where 1.0 is highest priority.
The priorities in this range are mapped to the operating system's priority values. A “typical” thread priority might be 0.5, but because the priority is determined by the kernel, there is no guarantee what this value actually will be.