AngularJS - ng-if example

HTML

<div ng-app="miniapp" ng-controller="Ctrl">
    <div ng-if="beenAdded(id) == false">
        <form id="formAddComment" name="formAddComment" novalidate>
          <textarea id="taAddComment" name="taAddComment" placeholder="Add a comment.." ng-model="new_comment" ng-maxlength="1000" ng-required="true"></textarea>
          <button type="button" ng-click="addComment(formAddComment)" ng-disabled="addCommentDisabled">Ok</button>
       </form>
    </div>
    <button type="button" ng-click="showForm()">Show</button>
</div>

JavaScript

var $scope;
var app = angular.module('miniapp', []);

function Ctrl($scope) {
    $scope.showDiv = true;
    $scope.beenAdded = function(){
        return $scope.showDiv;
    };
    $scope.showForm = function(){
     $scope.showDiv = false;
    }    
    $scope.addComment = function (formAddComment) {
     console.log('valid');
     if (formAddComment.$valid) {
        console.log('valid');
     }
   }
};