Split a camelcase string into separate words

NSString+SplitOnCapital.h

//
//  NSString+SplitOnCapital.h
//
//  Created by Draco Li on 2012-08-04.
//  Copyright (c) 2012 Draco Li. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface NSString (SplitOnCapital)

- (NSString *)splitOnCapital;

@end

NSString+SplitOnCapital.m

//
//  NSString+SplitOnCapital.m
//
//  Created by Draco Li on 2012-08-04.
//  Copyright (c) 2012 Draco Li. All rights reserved.
//

#import "NSString+SplitOnCapital.h"

@implementation NSString (SplitOnCapital)

- (NSString *)splitOnCapital
{
  // Make a index of uppercase character
  NSRange upcaseRange = NSMakeRange('A', 26);
  NSIndexSet *upcaseSet = [NSIndexSet indexSetWithIndexesInRange:upcaseRange];
  
  // Split our camecase word
  NSMutableString *result = [NSMutableString string];
  NSMutableString *oneWord = [NSMutableString string];
  for (int i = 0; i < self.length; i++) {
    char oneChar = [self characterAtIndex:i];
    if ([upcaseSet containsIndex:oneChar]) {
      // Found a uppercase char, now save previous word
      if (result.length == 0) {
        // First word, no space in beginning
        [result appendFormat:@"%@", [oneWord capitalizedString]];
      }else {
        [result appendFormat:@" %@", oneWord];
      }
      
      // Clear previous word for new word
      oneWord = [NSMutableString string];
    }
    
    [oneWord appendFormat:@"%c", oneChar];
  }
  
  // Add last word
  if (oneWord.length > 0) {
    [result appendFormat:@" %@", oneWord];
  }
  
  return result;
}

@end