编辑对传递参数的引用;t更新模型

我有一个表，它显示项目并允许内联编辑，并能够保存或放弃更改。

每个表行都包含列，这些列在未编辑行时显示项目的内容，在行处于编辑模式时显示用于编辑的输入。

这是HTML:

<table class="table table-bordered">
  <thead>
    <tr>
      <th>Field A</th>
      <th>Field B</th>
      <th>Field C</th>
      <th></th>
    </tr>
  </thead>
  <tbody>
    <tr ng-repeat="item in items">
      <td>
        <span ng-show="editingItem !== item">
          {{item.fieldA}}
        </span>
        <input type="text" ng-model="item.fieldA" class="form-control" ng-show="editingItem === item" />
      </td>
      <td>
        <span ng-show="editingItem !== item">
          {{item.fieldB}}
        </span>
        <input type="text" ng-model="item.fieldB" class="form-control" ng-show="editingItem === item" />
      </td>
      <td>
        <span ng-show="editingItem !== item">
          {{item.fieldC}}
        </span>
        <input type="text" ng-model="item.fieldC" class="form-control" ng-show="editingItem === item" />
      </td>
      <td>
        <i ng-click="startEditItem(item)" ng-show="editingItem !== item" class="fa fa-pencil link text-primary"></i>
        <i ng-click="confirmEditItem(item)" ng-show="editingItem === item" class="fa fa-check link text-success "></i>
        <i ng-click="cancelEditItem(item)" ng-show="editingItem === item" class="fa fa-times link text-danger"></i>
      </td>
    </tr>
  </tbody>
</table>

控制器代码：

angular.module('myApp', [])
  .controller('myController', function($scope) {
    $scope.items = [{
      id: '1',
      fieldA: 'foo1',
      fieldB: 'bar1',
      fieldC: 'baz1'
    }, {
      id: '2',
      fieldA: 'foo2',
      fieldB: 'bar2',
      fieldC: 'baz2'
    }, {
      id: '3',
      fieldA: 'foo3',
      fieldB: 'bar3',
      fieldC: 'baz3'
    }, ];
    $scope.startEditItem = function(item) {
      //clone, won't point to same reference
      $scope.editingItemCopy = JSON.parse(JSON.stringify(item));
      $scope.editingItem = item;
    }
    $scope.confirmEditItem = function() {
      $scope.editingItem = null;
      // no need to do anything, the model is changed already.
    }
    $scope.cancelEditItem = function(item) {
      $scope.editingItem = null;
      //below line doesn't work
      //item = JSON.parse(JSON.stringify($scope.editingItemCopy));
      for(var i = 0; i < $scope.items.length; i++) {
        if($scope.items[i].id === item.id) {
          $scope.items[i] = JSON.parse(JSON.stringify($scope.editingItemCopy));
        }
      }
    }

  });

我想知道为什么$scope.cancelEditItem中的注释行不起作用，如果传递给函数的参数应该指向数组中的同一元素，我必须修改$scope.items数组。

这是plunkerhttp://plnkr.co/edit/XF1ytvJ6HYfceaivZhfr?p=preview，可以随意取消对该行的注释，并对数组迭代进行注释，看看我在说什么。