NSMutableArray vs NSArray which is better

Question

This is a bit of a silly question, but if I want to add an object to an array I can do it with both NSMutableArray and NSArray, which should I use?

Answer 1

An NSArray object manages an immutable array—that is, after you have created the array, you cannot add, remove, or replace objects. You can, however, modify individual elements themselves (if they support modification). The mutability of the collection does not affect the mutability of the objects inside the collection. You should use an immutable array if the array rarely changes, or changes wholesale.

An NSMutableArray object manages a mutable array, which allows the addition and deletion of entries, allocating memory as needed. For example, given an NSMutableArray object that contains just a single dog object, you can add another dog, or a cat, or any other object. You can also, as with an NSArray object, change the dog’s name—and in general, anything that you can do with an NSArray object you can do with an NSMutableArray object. You should use a mutable array if the array changes incrementally or is very large—as large collections take more time to initialize.