Shuffling a greek word in iOS prints unknown symbols - ios

Question

I want to shuffle a string that contains Greek characters:
Here is my code:
- (void)shuffle {
NSLog(#"Will shuffle :%#",anagram2);
NSData* data = [anagram2 dataUsingEncoding:NSWindowsCP1253StringEncoding];
NSLog(#"after encoding :%#",anagram2);
NSString *someString = [[NSString alloc]initWithData:data encoding:NSWindowsCP1253StringEncoding];
NSLog(#"Greek word:%#",someString);
int length = anagram2.length;
NSMutableArray *letters = [[NSMutableArray alloc] init];
for (int i = 0; i< length; i++) {
NSString *letter = [NSString stringWithFormat:#"%c", [someString characterAtIndex:i]];
NSLog(#"Character:%#",letter);
[letters addObject:someLetter];
}
for (int i = 0; i<length; i++) {
int value = arc4random() % (length-1);
//NSLog(#"Value is : %i", value);
[letters exchangeObjectAtIndex:i withObjectAtIndex:value];
}
}
I can see the Greek word correctly. But the shuffling does not work. How can I extract each character and add it to a letters array. It works with English words but not with Greek ones, so I suppose that I should replace this:
NSString *letter = [NSString stringWithFormat:#"%c", [someString characterAtIndex:i]];
with something else.

Answer 1

The main problem seems to me that
[NSString stringWithFormat:#"%c":...]
works only with ASCII characters. You would have to use at least the "%C" format to make
it work with Unicode characters.
Also the conversion from NSString to NSData and back would fail as soon as you have any characters that are not available in the specified encoding.
The following method avoids all these problems and should work with arbitrary Unicode characters
(even with Emojis, which are internally represented as 2 UTF-16 characters):
NSString *string = #"Ελλάδα 😄";
NSLog(#"Will shuffle: %#", string);
// Convert string to an array of (32 bit) Unicode characters:
NSMutableData *data = [[string dataUsingEncoding:NSUTF32BigEndianStringEncoding] mutableCopy];
uint32_t *letters = [data mutableBytes];
int length = [data length]/4; // The number of 32-bit Unicode characters
// Shuffle the Unicode characters:
for (int i = 0; i<length; i++) {
int value = arc4random() % (length-1);
uint32_t tmp = letters[i];
letters[i] = letters[value];
letters[value] = tmp;
}
// Create new string from the shuffled Unicode characters:
NSString *shuffled = [[NSString alloc] initWithData:data encoding:NSUTF32BigEndianStringEncoding];
NSLog(#"Shuffled: %#", shuffled);
Output:
Will shuffle: Ελλάδα 😄
Shuffled: α😄άλλ Εδ