angularjs 1.0.8如何替换$ scope.form。$ setPristine

Question

我不知道在角稳定版1.0.8中我该怎么做。问题是在验证的形式，我把一个值，然后按重置按钮我有不必要的消息“无效的价格”（我知道该形式是$ dirty所以我应该设置$ pristne）。 在棱角1.1.1我可以打电话：

$scope.advertForm.$setPristne();

但是如何在角度1.0.8中替换它。

我的表格：

  <form ng-controller="AddAdvertController" name="advertForm" novalidate>
    <label>Price ($)</label>
    <input ng-model="newAdvert.price" type="number" name="price" min="100" required>
    <span ng-show="advertForm.price.$dirty && advertForm.price.$invalid">Invalid price</span>
    <br/>
    <button ng-click="reset()" ng-disabled="isUnchanged()">Reset</button>
    <button ng-click="add()" ng-disabled="advertForm.$invalid || isUnchanged()">Save</button>
  </form>

我的控制器：

motoAdsApp.controller('AddAdvertController', ['$scope',
  function($scope) {
    $scope.emptyAdvert = {
      price: null
    };

    $scope.add = function() {
      alert('User added!');
      $scope.reset();
    };

    $scope.reset = function() {
      $scope.newAdvert = angular.copy($scope.emptyAdvert);
      if ($scope.advertForm) {
        // In angular 1.1.1 or higher
        //$scope.advertForm.$setPristne();
        // How to do in angular 1.0.8?
      }
    };

    $scope.isUnchanged = function() {
      return angular.equals($scope.newAdvert, $scope.emptyAdvert);
    };

    $scope.reset();    
  }
]);

Example on Plunker