角度：选择以编程方式更改ng-model，但不会触发ng-change事件

Question

Here's my select element:

 <select class="small-3 columns end statSelect"
          ng-model="chart.categoryAxis"
          ng-change="renderMainChart()"
          ng-options="metric as metric.value for metric in chart.metrics()">
  </select>

I'm changing chart.categoryAxis programmatically every time I click on a button. However, the ng-change method renderMainChart() doesn't get called. Why is this?

Here's an example of one of the options:

<option label="Ad Started" value="object:33">Ad Started</option>

Depending on which button I click, that changes the ng-model value appropriately. But the ng-change function renderMainChart() doesn't get called.

Answer 1

Aelliott1485's answer can be implemented but it would need you to add an extra watch which may not be preferable always.

---

If you are using Angular 1.3 or higher then you can pass a function to the ng-model directive.

This allows you to specify a method instead of a variable in your ng-model attribute. The method should take an optional parameter. If an argument is passed it should store that value, if no argument is passed it should return a value.

In this case change your ng-model to call a function instead of accessing a property.

<select class="small-3 columns end statSelect"
      ng-model="chart.categoryAxis()"
      ng-change="renderMainChart()"
      ng-options="metric as metric.value for metric in chart.metrics()">    
</select>

and write a function like this in your controller

$scope.categoryAxis = function(value) {
    $scope.ca = value || $scope.ca; // You can also keep a local variable inside the controller instead of a property on $scope
    return $scope.ca;
};

NOTE: You may need to come up with better names.

Answer 2

You can utilize $watch() to handle the changing of the value, even when the user doesn't change the value using the select list. For example:

 var app = angular.module('plunker', []); app.controller('MainCtrl', function($scope) { var options = [{ value: 'a', id: 1 }, { value: 'b', id: 2 }]; $scope.debugOutput = ''; $scope.chart = { categoryAxis: options[0], metrics: function() { return options; } }; $scope.renderMainChart = function() { console.log('renderMainChart', arguments); }; $scope.pickA = function() { $scope.chart.categoryAxis = options[0]; }; $scope.pickB = function() { $scope.chart.categoryAxis = options[1]; }; $scope.$watch('chart.categoryAxis', function(newValue, oldValue) { $scope.debugOutput += 'categoryAxis changed ' + angular.toJson(oldValue) + ' to ' + angular.toJson(newValue) + "\\n"; }); }); 

 <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.23/angular.min.js"></script> <div ng-app="plunker"> <div ng-controller="MainCtrl"> <select class="small-3 columns end statSelect" ng-model="chart.categoryAxis" ng-change="renderMainChart()" ng-options="metric as metric.value for metric in chart.metrics()"></select> <div>Selected category Axis: <span>{{ chart.categoryAxis | json }}</span></div> <div> <input type="button" ng-click="pickA()" value="pickA" /> </div> <div> <input type="button" ng-click="pickB()" value="pickB" /> </div> <div>{{ debugOutput }}</div> </div> </div>