nsstring遍历汉子

NSString *mytimestr=@"好人一生平安";
    size_t length = [mytimestr length];
    for (size_t i=; i < length; i++) {
        unichar c = [mytimestr characterAtIndex:i];
        NSLog(@"%C", c);
    }

uitextfield获取中文：

      [self.tf addTarget:self action:@selector(textFieldDidChange:) forControlEvents:UIControlEventEditingChanged];

- (void)textFieldDidChange:(UITextField *)tf {
    NSMutableString *str = [NSMutableString string];
    if (tf.text.length > 0) {
        for (int i = 0; i<tf.text.length; i++) {
            unichar c = [tf.text characterAtIndex:i];
            if (c >=0x4E00 && c <=0x9FA5)
            {
                [str appendString:[tf.text substringWithRange:NSMakeRange(i, 1) ]];
            }
        }

    }
    NSLog(@"-------:%@",str);

}