AngularJS ng-style not changing with property

All we need is an easy explanation of the problem, so here it is.

I cant seem to figure out why the style property is not getting updated. In my larger application it seems to work fine.

angular.module('Model', [])
    .factory('SizeModel', function () {
        return {
            width: 200,
            height: 100,
            display:"block",
            getCombined: function() {
                return parseInt(this.width) + parseInt(this.height);
            }
        };
    });

function AlbumCtrl($scope,SizeModel) {
    $scope.master = SizeModel;
    $scope.$watch("master",function(){
    $scope.myprop = { display: $scope.master.display,
                      backgroundColor: "#333",
                      width: $scope.master.width+'px',
                      height: $scope.master.height+'px',
                      color: "#FFF"
                     };
        });

}

function AnoCtrl($scope,SizeModel) {
    $scope.master = SizeModel;

    $scope.toggle = function(){
        $scope.master.display = "none";
    }
}

function EditCtrl($scope,SizeModel) {
    $scope.master = SizeModel;
}

http://jsfiddle.net/ganarajpr/C2hRa/4/

Here is a fiddle which shows the issue I am currently facing. You will notice that the width and height are getting updated in the div when you change the input. But the style itself doesnt seem to be updating. Anyone can tell me what I am doing wrong here?

I have tried all the following scenarios

  1. using $scope.$apply.. – Throws an error stating $apply already in progress..
  2. $rootScope.$apply – same as above.
  3. Setting another variable in a service which is $watched in the other controller. – no change seen.

It would be really cool if someone can get me an answer to this. Also would be really happy if you can tell me why exactly it is not getting updated.

How to solve :

I know you bored from this bug, So we are here to help you! Take a deep breath and look at the explanation of your problem. We have many solutions to this problem, But we recommend you to use the first method because it is tested & true method that will 100% work for you.

Method 1

You had assigned the width and height values to the myprop style field on a one-off basis. So when you changed the width or height the myprop was not changing.

Change the myprop value to a function that computes its value instead…

http://jsfiddle.net/DyHHJ/

Method 2

Your $scope.$watch in the AlbumCtrl only watches reference inequality, which is determined by strict comparison via the !== Javascript operator. Because you are changing only a property on the object, the reference to master is still the same and doesn’t fire the $watch. You need to pass an additional argument to $watch to use objectEquality. See this plunkr, and here is the relevant code below:

$scope.$watch("master",function() {
  $scope.myprop = {
    display: $scope.master.display,
    backgroundColor: "#333",
    width: $scope.master.width+'px',
    height: $scope.master.height+'px',
    color: "#FFF"
  };
}, true);

The third argument true tells angular to determine inequality of the watchExpression by the angular.equals function. It correctly determines that the the updated master object has been changed, and updates myprop

Note: Use and implement method 1 because this method fully tested our system.
Thank you 🙂

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

Leave a Reply