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Should NSMutableArray be reversed when possible?

Suppose I have NSNumbers 1 through 450. I can add them to NSMutableArray starting from 1 and ending with 450, or starting from 450 and ending with 1. My code will be a little easier if I can start at 1 and end at 450, but when it finally comes to me to list the array, I will eventually need to cancel it. In other words, I need the first object in the enumeration to be 450, and the last to be 1.

Since my code will be simpler if I do it this way (add a start at 1 and then cancel it before listing), this is my preferred method. However, Apple's documentation for - (NSEnumerator *)reverseObjectEnumerator says:

It is more efficient to use the fast enumeration protocol (see NSFastEnumeration). Quick listing is available on Mac OS X v10.5 and later and iOS 2.0 and later.

So should I avoid array access and just write a little more complicated code so that NSMutableArray is created in the right order first?

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You can use quick enumeration with an NSEnumerator instance, the quick enumeration documentation even uses the reverseObjectEnumerator: method reverseObjectEnumerator: as an example:

 NSEnumerator *enumerator = [array reverseObjectEnumerator]; for (NSString *element in enumerator) { //... }

Also, your question sounds just like premature optimization ...

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No, you do not need to write more complex code to put it in the correct order. The reverseObjectEnumerator handler will work fine, it is only slightly slower. If performance is a big issue, then any of the snippets below will work well (the faster the while loop)

 // Assuming 'array' is your NSMutableArray int i = [array count]; while(i--) { Object *current = [array objectAtIndex:i]; // Mess around with current }

This will start you at level 450 and end at 0. You can also do this with a for loop, although you need to make sure that you either start at index 449 or do something like

 for(int i = [array count]; i > 0 ; i--) { Object *curreyt = [array objectAtIndex:i-1]; // Mess around with current }
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