Angular $Scope service: How does it work?

I've been experimenting with Angular for a couple of weeks and am a little bothered that I don't understand the magic employed by the $scope service. I've been successful in writing controllers that use the $scope service to update models/views and I've been able to write my own directives to do the same.

It's amazing! I just don't get what is going on under the hood with the $scope service. When I create something like the following, what is actually happening when I make the assignment to $scope.newproperty? I've not been able to find any documentation specific to the $scope service.

module.controller("menu_ctrl",['$scope','$http',function($scope,$http){
$scope.newproperty = "Bound to model!" //magic!
}]);

Furthermore, when I create a new link function within a directive (example below), how is it that all of a sudden I can just access the scope with a variable? I assume there's some magic going on employing the $scope or $apply services, but I'm just left guessing. Any help here would be much appreciated. Thanks!

srvcs.directive('directiv', ['$http',function($http) {
var returnObj = {
link: function linkfn(scopeVar, instance, attr){
console.log(scopeVar);
scopeVar.newproperty = "Also bound to model!" //more magic!
...
...
}
};
return returnObj;
}]);

`$scope` isn't a service *per se*; it's just a child scope of the application's root scope. So you should check out the [$rootScope service][1] documentation.

Technically speaking, a scope is an object that prototypically inherits from `$rootScope` and it's created using the `$new` method. Since it's an object, you can create new properties on it just by doing `$scope.property = value;`. No getter/setter methods under the hood. To understand it better you should look up `function $RootScopeProvider()` in Angular source code.

And since the scope is just an object, you can access it in the `link` function within a directive the same way you do it in controllers. No magic required. :)

About `$apply`, it's not a service either, but a method of the `$rootScope` service. All it does is trigger a digest cycle in order for Angular to process the watchers of the current scope and its children.

Finally, you might be interested in checking out this post on [understanding Angular scopes][2], in case you haven't already. :)


[1]:

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.$rootScope.Scope
[2]:

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