remove non ASCII characters from NSString in objective-c

Question

I have an app that syncs data from a remote DB that users populate. Seems people copy and paste crap from a ton of different OS's and programs which can cause different hidden non ASCII values to be imported into the system.

For example I end up with this:

Artist:â â Ioco

This ends up getting sent back into system during sync and my JSON conversion furthers the problem and invalid characters in various places cause my app to crash.

How do I search for and clean out any of these invalid characters?

Solution

While I strongly believe that supporting unicode is the right way to go, here's an example of how you can limit a string to only contain certain characters (in this case ASCII):

NSString *test = @"Olé, señor!";

NSMutableString *asciiCharacters = [NSMutableString string];
for (NSInteger i = 32; i < 127; i++)  {
    [asciiCharacters appendFormat:@"%c", i];
}

NSCharacterSet *nonAsciiCharacterSet = [[NSCharacterSet characterSetWithCharactersInString:asciiCharacters] invertedSet];

test = [[test componentsSeparatedByCharactersInSet:nonAsciiCharacterSet] componentsJoinedByString:@""];

NSLog(@"%@", test); // Prints @"Ol, seor!"

Comments

[Morten Fast]

No, because stringByTrimmingCharactersInSet only trims the ends of the string, and therefore won't remove all the characters.

[Besi]

I agree that Unicode is the way to go. However in some cases this might still be valid. I have to generate QR Codes and I think that umlauts and the like are not ideal characters there.

[Felipe]

Thanks, mate! This was brilliant.