The port type for an index value. The associated value can be an NSNumber object or any object that responds to the -intValue, -floatValue, or -doubleValue methods.
Available in Mac OS X v10.4 and later.
Declaration Syntax Version Information- Available in Monobjc Bridge: 10.6 (For Mac OS X 10.6 and later), 10.5 (For Mac OS X 10.5 and later)