Unfortunately, this is not correct; -[NSString characterAtIndex:]
returns a unichar, which is not a char. In addition, it will give
odd results for composed characters. Depending on what you want,
you might be able to use rangeOfComposedCharacterAtIndex:.
I'd also use NSMutableString instead of a stack buffer of chars,
since this looks like a buffer overflow (unless I'm missing
something):
I think this is definitely the way to go. Something like this
(untested, typed into Mail):
- (NSString*) reversedString
{
unsigned len = [self length];
NSMutableString* reversed = [NSMutableString stringWithCapacity:len];
unsigned charIdx = len;
while( charIdx > 0 ) {
NSRange charRng = [self rangeOfComposedCharacterSequenceAtIndex:
(charIdx - 1)];
[reversed appendString:[self substringWithRange:charRng]];
charIdx = charRng.location;
}
return reversed;
}
Naturally this will be horribly inefficient, as it creates a new
object for every composed character sequence, but the logic is likely
what an end-user would expect a reversed string to look like.
If you ever actually needed to optimize the string reversal you could
drop down to using a reasonably sized unichar buffer and
"getCharacters:inRange:" to do it in batches. I'm not sure how one
would best optimize the composed character sequences calculations,
but probably checking against +[NSCharacterSet nonBaseCharacterSet]
would be good enough.
~Martin
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