angular-360-no-scope 0 Bower npm

$watch controllerAs data without injecting $scope



$watch your controllerAs controller’s data, without injecting $scope.

How do I use it?

  • [npm|bower] install angular-360-no-scope
  • Include angular-360-no-scope.js in your app
  • Add a dependency on angular-360-no-scope to your app module.
  • Write your controller as usual, but avoid $scope
  • Utilize this.$watch() as needed

Live Demo



When using angular’s controllerAs, a controller is given a name and a reference to the controller is placed on the $scope. When writing the logic for the controller, data is typically stored directly on the controller itself, not on the $scope. When referencing the data from a template, the data is namespaced by the controllerAs name.

This provides various benefits, which help us write cleaner, more maintainable code. See the style guides by Todd Motto and John Papa for more details.

Still need $scope capabilities

One oddity of writing ControllerAs code is that we no longer tend to have the $scope reference handy. Besides being a tempting dumping ground for data, $scope also provides some important funtionality that we occasionally need such as $watch (and $on, $broadcast, and $emit).

A simple mechanism to provide those functions is to inject $scope into the controller function. Then, in order to watch your controller data, you may do something like so:

$scope.$watch(function() { return ctrl.someData }, callback)

This is a little clunkier than watching scope data, i.e., $scope.$watch("some.scope.variable", callback). Additionally, if you want to watch nested attributes whose parents may or may not be initialized, we might need to add yet another dependency on $parse so we must do something like:

$scope.$watch(function() { return $parse("some.controller.variable")(ctrl); }, callback);

360-no-scope makes this easier

With 360-no-scope, your controllers are decorated, and augmented with a $watch function. The $watch function is bound to the controller instance. This allows you to write ctrl.$watch("some.controller.variable", callback), much like the simple $scope.$watch you are already familiar with.

Sample Controller

app.controller("MyController", function () { // HERE, no $scope is necessary
  var ctrl = this;
  ctrl.watchCount = 0; = {};
  // Here is the "scope-less" watch registration.  Watching ""
  ctrl.$watch("", callback);  // <-- HERE, $watch something on the controller
  function callback (newVal, oldVal) { console.log("WatchCount: " + ctrl.watchCount++, newVal, oldVal); }

How does it work?

This lib decorates $controllerProvider.register and the $controller service. When a controller is registered with $controllerProvider, or when a controller is instantiated with the $controller() service, the controller fn passed in is augmented with a $watch function (as well as with $on, $broadcast, and $emit).

360-no-scope augments the controller fn by wrapping it in a surrogate controller which is executed instead. The surrogate is annotated with the same injectable dependencies as the real controller fn. Then, $scope is added to the dependency list. When angular instantiates the controller surrogate, the surrogate always gets $scope. It then builds the $scope passthrough functions and adds them to the real controller’s prototype. Finally, it instantiates and returns the real controller.

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