How to use jquery validate "depends" on rules other than "required"?

jquery, validation

Solution

The 2nd example in the documentation uses email:

$(".selector").validate({
  rules: {
    contact: {
      required: true,
      email: {
        depends: function(element) {
          return $("#contactform_email:checked")
        }
      }
    }
  }
});

In summary, that rule is saying "contact is required and it must be an email address if `#contactform_email` checkbox is checked".

So if you wanted to do that with a regex (or any parameter-requiring rule method), it looks like this:

        minlength: {
            param:6,
            depends: function (element) {
                return $('#len').is(':checked');
            }
        }

Which says "The min length is 6 but only when the `#len` checkbox is checked".

See it in action here: http://jsfiddle.net/ryleyb/8Nsm3/

Problem

Every example of "depends" I can find on the web uses the "required" rule. Clearly this is not sufficient. How do I use the "depends" clause with, for example, a "regex" rule? I have two radio buttons, if one is selected, I regex-validate a textbox. If the other is selected, I don't care what is in the textbox.

Original source