ios：字符串与汉字的判断

//判断输入的城市是汉字还是字母    for (int i = 0; i < cityStr.length; i ++) {        NSRange range = NSMakeRange(i, 1);        NSString* subString = [cityStr substringWithRange:range];        const char* cString = [subString UTF8String];        if (strlen(cString) != 3) {            //strlen(cString) == 3 是汉字 strlen(cString) ==1 是字母            UIAlertView* alert = [[UIAlertView alloc] initWithTitle:@"提示" message:@"城市不能为字母" delegate:self cancelButtonTitle:nil otherButtonTitles:@"确定", nil];            [alert show];            return;        }    }