title: Knockout Validation disable validation
body: <p>I have ko.observableArrays with validation on the items. The user can mark a item as deleted. When it is marked as deleted, I need to disable validation on that item.</p>
  
  <p>How do you dynamically disable validation?</p>
  
  <p>Example: <a href="http://jsfiddle.net/3RZjT/2/" rel="noreferrer">http://jsfiddle.net/3RZjT/2/</a></p>
  
  <pre><code>&lt;div data-bind="foreach: names"&gt;
      &lt;input data-bind="value: name, valueUpdate: 'afterkeydown'" /&gt; &lt;a data-bind="click: deleteMe, text:deleted()?'undelete':'delete'" href="#"&gt;delete&lt;/a&gt;&lt;br/&gt;
  &lt;/div&gt;
  
  function Person(name){
      var self = this;
      self.name = ko.observable(name).extend({ required: true});
      self.deleted = ko.observable(false);
      self.deleteMe = function(){ 
          self.deleted(!self.deleted());
          self.deleted.extend({ validatable: !self.deleted()});
      };
  }
  
  var viewModel = {
      names: ko.observableArray([new Person("Ken"), new Person("")])
  };
  
  ko.applyBindings(viewModel);
  </code></pre>