CocoaでURLエンコード

@implementation NSString (URLEncoding)
 
-(NSString *)stringByURLEncoding:(NSStringEncoding)encoding
{
  NSArray *escapeChars = [NSArray arrayWithObjects:
             @";" ,@"/" ,@"?" ,@":"
            ,@"@" ,@"&" ,@"=" ,@"+"
            ,@"$" ,@"," ,@"[" ,@"]"
            ,@"#" ,@"!" ,@"'" ,@"("
            ,@")" ,@"*"
            ,nil];
 
  NSArray *replaceChars = [NSArray arrayWithObjects:
              @"%3B" ,@"%2F" ,@"%3F"
             ,@"%3A" ,@"%40" ,@"%26"
             ,@"%3D" ,@"%2B" ,@"%24"
             ,@"%2C" ,@"%5B" ,@"%5D"
             ,@"%23" ,@"%21" ,@"%27"
             ,@"%28" ,@"%29" ,@"%2A"
             ,nil];
 
  NSMutableString *encodedString = [[[self stringByAddingPercentEscapesUsingEncoding:encoding] mutableCopy] autorelease];
 
  for(int i=0; i<[escapeChars count]; i++) {
    [encodedString replaceOccurrencesOfString:[escapeChars objectAtIndex:i]
                                   withString:[replaceChars objectAtIndex:i]
                                      options:NSLiteralSearch
                                        range:NSMakeRange(0, [encodedString length])];
  }
 
  return [NSString stringWithString: encodedString];
}
 
@end