Making an array of integers in Objective-C

Question

If you want to make an array of integers, can you use NSInteger? Do you have to use NSNumber? If so, then why?

Answer 1

You can use a plain old C array:

NSInteger myIntegers[40];

for (NSInteger i = 0; i < 40; i++)
    myIntegers[i] = i;

// to get one of them:
NSLog (@"The 4th integer is: %d", myIntegers[3]);

Or, you can use an NSArray or NSMutableArray, but here you will need to wrap up each integer inside an NSNumber instance (because NSArray objects are designed to hold class instances).

NSMutableArray *myIntegers = [NSMutableArray array];

for (NSInteger i = 0; i < 40; i++)
    [myIntegers addObject:[NSNumber numberWithInteger:i]];

// to get one of them:
NSLog (@"The 4th integer is: %@", [myIntegers objectAtIndex:3]);

// or
NSLog (@"The 4th integer is: %d", [[myIntegers objectAtIndex:3] integerValue]);

Answer 2

If you want to use a NSArray, you need an Objective-C class to put in it - hence the NSNumber requirement.

That said, Obj-C is still C, so you can use regular C arrays and hold regular ints instead of NSNumbers if you need to.