NSString+charactersAsArray.h

#import <Foundation/Foundation.h>

@interface NSString (charactersAsArray)

- (NSArray *)charactersAsArray;

@end

NSString+charactersAsArray.m

#import "NSString+charactersAsArray.h"

@implementation NSString (charactersAsArray)

- (NSArray *)charactersAsArray
{
    NSMutableArray *characters = [NSMutableArray arrayWithCapacity:[self length]];
    for (int i = 0; i < [self length]; i++)
        [characters addObject:[self substringWithRange:NSMakeRange(i, 1)]];
    return characters;
}

@end