当新值为空时，恢复ng-model的旧值

Question

我有一个json，我用它来填充angularjs中的表，并使表行可编辑以更新值，但如果值为空，那么我想恢复旧值。我试图使用临时变量来实现这一点，但是当我使用$scope设置变量时，我得到的错误是：

  

$ scope.singleConfig.value未定义。

<tr ng-repeat="singleConfig in allConfigDatabase.data | filter:searchParameter|orderBy:orderByField:reverseSort" ng-style="{'background-color':(singleConfig.db == 'true'?'white':'gray')}">
    <td >{{singleConfig.parameter}}</td>
    <td >
        <div ng-hide="editingData[singleConfig.id]"
            style="padding-bottom: 10px">{{singleConfig.value}}</div>
        <div ng-show="editingData[singleConfig.id]"
            style="padding-bottom: 10px">
            <input type="text" ng-model="singleConfig.value">
        </div>
         <span class="updateButton">
            <button ng-hide="editingData[singleConfig.id]"
                ng-click="modify(singleConfig);oldValue(singleConfig.value)" class="updateButton">
                <span class="glyphicon glyphicon-pencil"></span>
            </button>
    </span> 
        <button ng-show="editingData[singleConfig.id]"
            ng-click="update(singleConfig);updateConfig(singleConfig.parameter,singleConfig.value,updateDatabaseCheck)">Save</button>
        <input type="checkbox" id="updateCheckbox"
        ng-model="updateDatabaseCheck" ng-show="editingData[singleConfig.id]"> <label
        for="updateCheckbox" ng-show="editingData[singleConfig.id]">Save
            in Database</label>
        <button ng-show="editingData[singleConfig.id]"
            ng-click="update(singleConfig);singleConfig.value=getOldValue();reset()">Close</button>

    </td> 
</tr>

控制器中的

$scope.updateConfig = function(
   updateParameter, updateValue,updateCheck) {
    if (checkInputValidity(updateParameter,
            updateValue)) {
        if (updateCheck == true) {
            addOrUpdateTable(
                    updateParameter,
                    updateValue, "true");
            showNotification('**Your Value has been updated in database**','green',updateParameter,updateValue);
        } else {
            addOrUpdateTable(
                    updateParameter,
                    updateValue, "false");
            showNotification('**Your Value has been updated in memory**','red',updateParameter,updateValue);
        }
    } else {
        $scope.singleConfig.value=trackOldValue;//for this line getting an error
        showNotification('**Your value field was empty**','red',null,null);

    }
}