µBio µBio - 5 months ago 16
AngularJS Question

$watch not firing on data change

I have a watch setup against the model of a ui-select2 dropdown (from ui-bootstrap). The watch fires on load but not on data changes and I can't figure out why.

It isn't the usual problem of not $apply'ing the model change or not using the third parameter for equality comparison (at least from my code).

What do I need to do to get it to fire?

Here is a plunk demonstrating the issue.

Answer

I fixed some stuff.

http://plnkr.co/edit/5Zaln7QT2gETVcGiMdoW?p=preview

The JS

var myMod = angular.module("myApp",[]).controller("MainController",  function($scope){
  $scope.myModel = {selectedId:null};
}).controller("DetailController",function($scope){
  $scope.items = [1,2,3,4];

  $scope.watchHitCount = 0;
  $scope.$watch('myModel.selectedId', function(newVal, oldVal){
    console.log(newVal + " " + oldVal);
    $scope.watchHitCount++;
  },true);
});

The index.html

  <body ng-app="myApp">
    <div ng-controller="MainController">
      <ng-include src="'detail.html'" ng-controller="DetailController"></ng-include>
    </div>
  </body>

The detail.html

<pre>watch hit: {{watchHitCount}}</pre>
<pre>selected value: {{myModel.selectedId}}</pre>
<select ng-model="myModel.selectedId" ui-select2="">
  <option></option>
  <option ng-repeat="item in items" value="{{item}}">{{item}}</option>
</select>

It was complaining about not finding the controller so I set it up the way I normally would with a named ng-app and a module declared that has controllers defined on it.

I also added an object to hold the value in your model. It is bad practice to use the $scope object as your model, instead your scope should refer to an object that is your model.

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