Handling data binding in AngularJS Services

Question

I'm trying to figure out how you handle binding properly when my data is stored in a service.

I can get things working if it put the service into the $scope and then get the templates to bind directly into it but that seems like a really bad idea.

I'd basically like to have it so that my views / controllers are able to easily change the state down in a service and have that reflected everywhere.

It feels like I should be able to do something like the following, but it doesn't work (http://jsfiddle.net/aidankane/AtRVD/1/).

HTML

<div ng-controller="MyCtl">
    <select ng-model="drawing" ng-options="d.file for d in drawings"></select>
</div>
<div ng-controller="MyOtherCtl">
    {{ drawing }}
</div>

JS

var myApp = angular.module('myApp', []);

myApp.factory('myService', function(){
    var me = {
        drawings: [{'file':'a'}, {'file':'b'}]
    };
    // selected drawing
    me.drawing = me.drawings[0];
    return me;
});

function MyCtl($scope, myService){
    // can do:
    // $scope.mys = myService;
    // and then in html ng-model="mys.drawing"
    // but that seems wrong

    $scope.drawings = myService.drawings;
    $scope.drawing = myService.drawing;

    // can I not do this? it doesn't seem to work anyway...
    $scope.$watch('drawing', function(drawing){
        myService.drawing = drawing;
    });
}

function MyOtherCtl($scope, myService){
    $scope.drawing = myService.drawing;
}

MyCtl.$inject = ['$scope', 'myService'];
MyOtherCtl.$inject = ['$scope', 'myService'];

Answer 1

You can bind to services using $watch and passing a function:

$scope.$watch( function () { return myService.drawing; }, function ( drawing ) {
  // handle it here. e.g.:
  $scope.drawing = drawing;
});

And then use $scope.drawing in your templates and they will automatically update:

<div ng-controller="MyOtherCtl">
  {{ drawing }}
</div>