Loop through NSMutableArray of custom objects in the most memory efficient way

Question

What is the most memory efficient way to loop through an NSMutableArray of custom objects? I need to check a value in each object in the array and return how many of that type of object is in the array.

Answer 1

for (WhateverYourClassNameIs *whateverNameYouWant in yourArrayName) {
    [whateverNameYouWant performSelector];
    more code here;
}

It's called fast enumeration and was a new feature with Objective C 2.0, which is available on the iPhone.