Allowing special characters in iOS - ios

Question

I am allowing the user to input some data into the TextField. The user inputs Š1234D into the TextField.
The code I have looks like this:
NSString *string = textField.text;
for (int nCtr = 0; nCtr < [string length]; nCtr++) {
const char chars = [string characterAtIndex:nCtr];
int isAlpha = isalpha(chars);
}
string output looks like this:Š1234D
Then I printed the first chars value, it looks like this:'`' instead of 'Š'. Why is this so? I would like to allow special characters in my code as well.
Any suggestion would be welcome as well. Need some guidance. Thanks

Answer 1

You are truncating the character value as [NSString chatacterAtIndex:] returns unichar (16-bit) and not char (8-bit). try:
unichar chars = [string characterAtIndex:nCtr];
UPDATE: Also note that you shouldn't be using isalpha() to test for letters, as that is restricted to Latin character sets and you need something that can cope with non-latin characters. Use this code instead:
NSCharacterSet *letterSet = [NSCharacterSet letterCharacterSet];
NSString *string = textField.text;
for (NSUIntger nCtr = 0; nCtr < [string length]; nCtr++)
{
const unichar c = [string characterAtIndex:nCtr];
BOOL isAlpha = [letterSet characterIsMember:c];
...
}

Answer 2

characterAtIndex: returns a unichar (2-byte Unicode character), not char (1-byte ASCII character). By casting it to char, you are getting only one of the two bytes.
You should turn on your compiler warnings. I believe "Suspicious implicit conversions" should do the trick.
On a separate note, you can't use isAlpha(char) with a unichar. Use [[NSCharacterSet letterCharacterSet] characterIsMember:chars]