When is it better to use an NSSet over an NSArray?

Question

I have used NSSets many times in my apps, but I have never created one myself.

When is it better to use an NSSet as opposed to an NSArray and why?

Answer 1

The best answer is to this is Apple's own documentation.

The main difference is that NSArray is for an ordered collection and NSSet is for an unordered collection.

There are several articles out there that talk about the difference in speed between the two, like this one. If you're iterating through an unordered collection, NSSet is great. However, in many cases, you need to do things that only an NSArray can do, so you sacrifice the speed for those abilities.

NSSet

• Primarily access items by comparison
• Unordered
• Does not allow duplicates

NSArray

• Can access items by index
• Ordered
• Allows duplicates

That's all there really is to it! Let me know if that helps.