How to find out whether a keyCode corresponds to an actual character or a function key?

Question

Below is my code. But how do I know whether the character is from an alphabet? (Any alphabet, not just a-z)

- (void)keyDown:(NSEvent *)theEvent
{
    NSString * const character = [theEvent charactersIgnoringModifiers];
}

Answer 1

You can use NSCharacterSet:

- (void)keyDown:(NSEvent *)theEvent
{
    NSString * const character = [theEvent charactersIgnoringModifiers];
    if ([character length] > 0)
    {
        unichar c = [character characterAtIndex:0];
        NSCharacterSet *letters = [NSCharacterSet letterCharacterSet];
        if ([letters characterIsMember:c])
        {
            NSLog(@"that's a letter!");
        }
    }
}

If you are calling this code frequently it might pay to store letters as an instance variable.