Question

How can I take two NSArrays, compare them, then return the number of differences, preferably the number of different objects, for example:

Array 1:
one
two
three

Array 2:
two
four
one

I would like that to return “1”

Answer 1

You can do this by using an intermediate NSMutableArray:

NSArray *array1 = [NSArray arrayWithObjects:@"One", @"Two", @"Three", nil];
NSArray *array2 = [NSArray arrayWithObjects:@"Two", @"Four", @"One", nil];
NSMutableArray *intermediate = [NSMutableArray arrayWithArray:array1];
[intermediate removeObjectsInArray:array2];
NSUInteger difference = [intermediate count];

With that way, only common elements will be removed.