Making an array of integers in iOS

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

C array:

NSInteger array[6] = {1, 2, 3, 4, 5, 6};

Objective-C Array:

NSArray *array = @[@1, @2, @3, @4, @5, @6];
// numeric values must in that case be wrapped into NSNumbers

Swift Array:

var array = [1, 2, 3, 4, 5, 6]

This is correct too:

var array = Array(1...10)

---

NB: arrays are strongly typed in Swift; in that case, the compiler infers from the content that the array is an array of integers. You could use this explicit-type syntax, too:

var array: [Int] = [1, 2, 3, 4, 5, 6]

---

If you wanted an array of Doubles, you would use :

var array = [1.0, 2.0, 3.0, 4.0, 5.0, 6.0] // implicit type-inference

or:

var array: [Double] = [1, 2, 3, 4, 5, 6] // explicit type

Answer 2

If the order of your integers is not required, and if there are only unique values

you can also use NSIndexSet or NSMutableIndexSet You will be able to easily add and remove integers, or check if your array contains an integer with

- (void)addIndex:(NSUInteger)index
- (void)removeIndex:(NSUInteger)index
- (BOOL)containsIndexes:(NSIndexSet *)indexSet

Check the documentation for more info.

Answer 3

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 4

I created a simple Objective C wrapper around the good old C array to be used more conveniently: https://gist.github.com/4705733

Answer 5

I think it's a lot easier to use NSNumbers. This all you need to do:

NSNumber *myNum1 = [NSNumber numberWithInt:myNsIntValue1];
NSNumber *myNum2 = [NSNumber numberWithInt:myNsIntValue2];
.
.
.
NSArray *myArray = [NSArray arrayWithObjects: myNum1, myNum2, ..., nil];

Answer 6

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.