javascript - Give angular directive a model name to access it's scope in the parent -

i'm trying access isolated scope of directive using model attribute on it's element when use in html. eg.

<div controller="parent">     <hello-world data-ng-model="hw"/>     <input type="submit"/> </div> 

the controller parent:

function($scope){   $scope.submit = function(){     alert($scope.hw.t);   } }; 

the directive hello-world:

app.directive('helloworld', function() {   return {      link: function(scope, element, attrs){       scope.t = 'test';     },      replace: true,      restrict: 'e',      scope: {},      template: '<h5>hello world {{t}}</h4>'   }; }); 

t defined in isolated scope, because displayed correctly. however, when click submit button, error because hw undefined. (because hello-world scope isn't being assigned 'hw' scope variable of parent. how can let hw defined scope of hello-world directive? use case make date picker exposes date picked through it's scope. like

<date-picker ng-model="date1"/> <date-picker ng-model="date2"/> 

in directive's scope, ensure month, year, etc. defined. in parent controller, can use $scope.date1.month , similar access date picked.

following comments, seems need make custom validateable elements using ngmodel.

according ngmodel's documentation, can done using manually ngmodelcontroller. following page should contain information need (look @ script.js in example): https://docs.angularjs.org/api/ng/type/ngmodel.ngmodelcontroller

good luck.

an example of directive works ngmodel