iOS how does NSMutableArray check if it contains NSNumber objects?

Question

I'm writing some code that will be using NSMutableArray and storing int values within it, wrapped within NSNumbers.

I would like to confirm that querying an iOS NSArray or NSMutableArray using new NSNumbers with same values is legal , of if I need to explicitly iterate over the array, and check if each int value is equal to the value I want to test against?

This appears to work:

NSMutableArray* walkableTiles = [NSMutableArray array];    


[walkableTiles addObject:@(1)];
[walkableTiles addObject:@(2)];
[walkableTiles addObject:@(3)];


if([walkableTiles containsObject:@(1)])
{
    DLog(@"contains 1"); //test passes
}
if([walkableTiles containsObject:[NSNumber numberWithFloat:2.0]])
{
    DLog(@"contains 2");//test passes
}
if([walkableTiles containsObject:[NSNumber numberWithInt:3]])
{
    DLog(@"contains 3");//test passes
}

Answer 1

What you are doing is fine. Why wouldn't it be?

The containsObject: method actually iterates over the array and calls the isEqual: method on each object passing in the object you are checking for.

BTW - there is nothing special here about using NSNumber . It's the same with an array of any object type. As long as the object's class has a valid isEqual: method, it will work.

Answer 2

Per the Apple's NSNumber documentation , you should use isEqualToNumber :

isEqualToNumber: Returns a Boolean value that indicates whether the receiver and a given number are equal. - (BOOL)isEqualToNumber:(NSNumber *)aNumber