NSComparisonResult and NSComparator - what are they?

Question

What is NSComparisonResult and NSComparator?

I\'ve seen one of the type definitions, something like that:

typedef NSComparisonR         


        

Answer 1

Jacob's answer is good, however to answer the part about "how is this different than a function pointer?":

1) A block is not a function pointer. Blocks are Apple's take on how to make functions first class citizens in C/C++/Objective-C. It's new to iOS 4.0.

2) Why introduce this strange concept? Turns out first class functions are useful in quite a few scenarios, for example managing chunks of work that can be executed in parallel, as in Grand Central Dispatch. Beyond GCD, the theory is important enough that there are entire software systems based around it. Lisp was one of the first.

3) You will see this concept in many other languages, but by different names. For example Microsoft .Net has lambdas and delegates (no relation to Objective-C delegates), while the most generic names are probably anonymous functions or first class functions.