Open Radar

 
Summary:
On many projects I'm working on, I sometimes need to return a pair of objects from a function/method.
Returning a `NSArray` or `NSDictionary` is always possible, of course, but it's not really suitable.

It would be great if the `Foundation` framework had support for a `NSPair` class, acting like `std::pair` in C++.  
It's of course easy to implement, but I think `Foundation` would really benefit having such a class.

Something like:

    @interface NSPair< __covariant FirstType, __covariant SecondType >: NSObject < NSCoding, NSCopying >
    
    @property( atomic, readwrite, strong, nullable ) FirstType first;
    @property( atomic, readwrite, strong, nullable ) SecondType second;
    
    - ( instancetype )initWithFirstValue: ( nullable FirstType )first secondValue: ( nullable SecondType )second NS_DESIGNATED_INITIALIZER;
    
    @end

Attached is a proposed implementation.