Fixing jQuery Validation with changing validators

Got jQuery Validation running, and now I know that it requires every input and select to have a name property; otherwise it will simply ignore your validation rules:

jquery.validate.js line 130:
staticRules[element.name] = existingRules;

It will however still apply the CSS-based rules, so finding that out was a bit tricky.

Next stop: I create a dialog with a dropdown to select some sort of object type, each object type having different attributes and different validation rules.

Of course, the validation rules have to be re-defined every time the dropdown value changes. If there is already a validator defined on the form, you need to destroy the existing validator

var form = $('#myForm).get(0);
$.removeData(form, 'validator');

(found here)

Still, some mysterious bit of code still remains, as validation is still executed even though the validator had been deleted and the dropdown is ignored in the (non-existing?) validator:

Uncaught TypeError: Cannot read property 'settings' of undefined
 jquery.validate.js:315

says Chrome, and IE reports

Unable to get value of the property 'settings': object is null or undefined

The culprit is the method delegate() (line 313), which does not check whether a validator exists:

function delegate(event) {
  var validator = $.data(this[0].form, "validator"),
  eventType = "on" + event.type.replace(/^validate/, "");
  // this fixes handling the deleted validator:
  if (!validator) return;
  validator.settings[eventType] && validator.settings[eventType].call(validator, this[0], event);
}