Add string method to NSIndexSet (pretty print NSIndexSet)

NSIndexSetStringAddition.m

#import <Foundation/Foundation.h>

NSString *indexSetToString(NSIndexSet *indexSet)
{
    NSMutableString *s = [[NSMutableString alloc] init];
    __block NSString *sep = @"";

    [indexSet enumerateRangesUsingBlock:
        ^void (NSRange range, BOOL *stop) {
            switch (range.length) {
                case 0: 
                    return;
                case 1: 
                    [s appendFormat:@"%@%ld", sep, range.location];
                    break;
                default: 
                    [s appendFormat:@"%@%ld-%ld", 
                        sep,
                        range.location,
                        range.location + range.length - 1];
                    break;
            }
            sep = @" ";
    }];
    return [NSString stringWithFormat:@"[%@]", s];
}

@implementation NSIndexSet (NSIndexSetStringAddition)
- (NSString *)string {
    return indexSetToString(self);
}
@end