iPhone Foundation - performance implications of mutable and xxxWithCapacity:0
- by Adam Eberbach
All of the collection classes have two versions - mutable and immutable, such as NSArray and NSMutableArray. Is the distinction merely to promote careful programming by providing a const collection or is there some performance hit when using a mutable object as opposed to immutable?
Similarly each of the collection classes has a method xxxxWithCapacity, like
[NSMutableArray arrayWithCapacity:0]. I often use zero as the argument because it seems a better choice than guessing wrongly how many objects might be added. Is there some performance advantage to creating a collection with capacity for enough objects in advance? If not why isn't the function something like + (id)emptyArray?
