Returns a new array containing the receiving array’s elements that are not present in another array.

NSArray-SCRAdditions.m

@interface NSArray (SCRAdditions)
- (NSArray*)objectsNotInArray:(NSArray*)array;
@end

@implementation NSArray (SCRAdditions)

- (NSArray*)objectsNotInArray:(NSArray*)array {
    NSMutableArray* list = [[NSMutableArray alloc] init];
    [self enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL* stop) {
        if ([array containsObject:obj]) {
            return;
        }
        [list addObject:obj];
    }];
    return list;
}

@end