只要在 textViewDidChange 方法中先對 text 進行判斷一下就 OK 了

-(BOOL)isSudoku:(NSString *)str{
    NSString *other = @"????????";
    NSString *lastStr = [str substringFromIndex:str.length-1];
    if (![other containsString:lastStr]) {
        return NO;
    }
    
    unsigned long len=lastStr.length;
    for(int i=0; i<len; i++)
    {
        unichar a=[lastStr characterAtIndex:i];
        if(!((isalpha(a))
             ||(isalnum(a))
             ||((a=='_') || (a == '-'))
             ||((a >= 0x4e00 && a <= 0x9fa6))
             ||([other rangeOfString:lastStr].location != NSNotFound)
             ))
            return NO;
    }
    return YES;
}