Cocoa NSArray/NSSet: -makeObjectsPerformSelector: vs. fast enumeration

Question

I want to perform the same action over several objects stored in a NSSet.

My first attempt was using a fast enumeration:

for (id item in myS         


        

Answer 1

I would argue for using makeObjectsPerformSelector, since it allows the NSSet object to take care of its own indexing, looping and message dispatching. The people who wrote the NSSet code are most likely to know the best way to implement that particular loop.

At worst, they would simply implement the exact same loop, and all you gain is slightly cleaner code (no need for the enclosing loop). At best, they made some internal optimizations and the code will actually run faster.

The topic is briefly mentioned in Apple's Code Speed Performance document, in the section titled "Unrolling Loops".

If you're concerned about performance, the best thing to do is set up a quick program which performs some selector on the objects in a set. Have it run several million times, and time the difference between the two different cases.