title: Angularjs dynamic ng-pattern validation
body: <p>I have a form that if a checkbox is false enforces validation on a text input using the ng-required directive.  If the checkbox is true, the field is hidden and the ng-required is set to false.</p>
  
  <p>The problem is that I also have a regex for validation specified on the input as well utilizing the ng-pattern angular directive.  The issue I am running into is that if a user fills in an invalid phone number, checks the box to deactivate that input (and consequently needs no further validation) the form will not allow submission as it is invalid based on the ng-pattern.</p>
  
  <p>I attempted to resolve this issue by adding an ng-change function to set the input model to null, however the ng-pattern and thus the field is still set to invalid on the initial set of the checkbox to false.  If I however uncheck the box, setting everything back to initial form load, then check the box again, the form is valid and able to submit.  I am not sure what I am missing.  Here is the ng-change code I have thus far:</p>
  
  <pre><code>    var phoneNumberRegex = /^\(?(\d{3})\)?[ .-]?(\d{3})[ .-]?(\d{4})$/;
      $scope.phoneNumberPattern = phoneNumberRegex;
      $scope.removeValidation = function() {
          if ($scope.cell._newUser === false) {
              $scope.request._number = '';
              $scope.phoneNumberPattern = /[0-9a-zA-Z]?/;
          } else {
              $scope.phoneNumberPattern = phoneNumberRegex;
          }
      };
  </code></pre>