In AngularJS, how to force the re-validation of a field in a form when another value in the same form is changed? -

i have form few fields, select , input field coupled: validation on input depends on value user chooses in select field.

i'll try clarify example. let's select contains names of planets:

<select id="planet" class="form-control" name="planet" ng-model="planet" ng-options="c.val c.label c in planets"></select> 

in input apply custom validation via custom directive named "input-validation":

<input id="city" input-validation iv-allow-if="planet==='earth'" class="form-control" name="city" ng-model="city" required> 

where directive:

.directive('inputvalidation', [function() {   return {     require: 'ngmodel',     restrict: 'a',     scope: {       ivallowif: '='     },     link: function(scope, elm, attrs, ctrl) {       ctrl.$parsers.unshift(function(viewvalue) {          //input allowed if attribute not present or expression evaluates true         var inputallowed = attrs.ivallowif === undefined || scope.$parent.$eval(attrs.ivallowif);          if (inputallowed) {           ctrl.$setvalidity('iv', true);           return viewvalue;         } else {           ctrl.$setvalidity('iv', false);           return undefined;         }        });     }   }; }])  

the full example can examined in plnkr: http://plnkr.co/edit/t2xmpy1ehvfa5knedfrf?p=preview

whenever select modified, need input verified again. not happening in code. doing wrong?

i have done same thing validation of start-date on change of end-date. in directive of start-date add watch change of end-date , call ngmodel.$validate() in case end-date new value defined.

    scope.$watch(function () {         return $parse(attrs.enddate)(scope);     }, function () {         ngmodel.$validate();     }); 

the important part take call ngmodel.$validate() inside directive.

note should use $validators custom validations above work. read here, $parsers old way - angularjs 1.3 use $validators

fixed plunker link