jQuery validation this.optional(element) always false

Question

Hi there. I'm trying to get familiar with jQuery validation custom methods and seems to get confused a bit. why this.optional(element) inside my custom method always returns false?

here is an example of my code:

<script type="text/javascript">
    $(document).ready(function(){
        $.validator.addMethod('customemethod', function(val, el){
            return this.optional(el) || false;
        }, 'custom method says its INVALID !');
        $('#myform').validate({ignore: '*[ignore]'});
        $('#validate').click(function(){
            $('#result').text($('#myform').validate().form());
            return false;
        });
    });
</script>
<form id="myform">
    <div><input type="text" id="customfield" name="customfield" /></div>
    <script type="text/javascript">
        $(document).ready(function(){$('#customfield').rules('add', { required: true, customemethod: true } ) } );
    </script>
    <div><input type="text" id="customfield2" name="customfield2" /></div>
    <script type="text/javascript">
        $(document).ready(function(){$('#customfield2').rules('add', { required: false, customemethod: true } ) } );
    </script>

    <div id="result"></div>
    <input id="validate" type="submit" />
</form>

in case if element is not required and it's value is not empty - validation method is called and i need to return true in this case. But this.optional(el) is always false :(

How can i solve it ? How can i check if element is required or not inside custom method? Thanks.