How to pass string and bool variables automatically to directive parent scope - angularjs

Question

I bind variable in a directive like this :
<path-filter-modal is-opened="filterModalIsOpened">
And in the directive I use '=' binding like this:
scope: {
isOpened: '='
}
When I change variable in directive, a parent scope contains own value.
How can I make that the parent scope contain the same value?
For objects it works well but not with strings and booleans.
Notice that I use controller that is defined in my directive in my directive to change values.

Answer 1

Because JavaScript is designed to be so.
Defining an isolate scope in the directive creates a new $scope object, which is a separate $scope object. Its only relationship with the parent scope is that: $isolateScope.$parent === $parentScope. It doesn't inherits from $parentScope prototypical.
When you assign some primitive type (string/boolean) to $scope.isOpened, actually JavaScript engine will create a new variable isOpened on $scope. It is totally not related to $parentScope.isOpened.
But now, Angular syncs the two variables for you implicitly. So binding primitive variables still makes two-way binding work well. Please check JSFiddle.
If you binds to some object type, the child scope and parent scope are referencing to the exactly the same copy of an object in the memory. Changing on the parent scope will change the child scope automatically. So two-way binding is always recommended to bind objects, not primitive types.
Check this JSFiddle. I bind a primitive and an object to the directive myDirective. Then modify them inside the link function:
scope.primitiveParam = 'primitive from directive';
// $parent.primitive and primitiveParam refer to different memory;
// Angular is responsible to sync them.
console.log(scope.$parent.primitive);
console.log(scope.primitiveParam);
scope.objectParam.name = 'object from directive';
// $parent.obj and objectParam refer to an identical object
console.log(scope.$parent.obj.name);
console.log(scope.objectParam.name);
console.log(scope.objectParam === scope.$parent.obj);
And the result is like:
primitive from parent
primitive from directive
object from directive
object from directive
For more details: Understanding Scopes (here are many intuitive images illustrating the concepts clearly)

Answer 2

RE: For objects it works well but not with strings and booleans
I think it's the usual case of prototypal inheritance problem. When the model come from object it works well, but if it come from non-objects there's a possibility that the ng-model is created on child scope.
To solve that problem, use modern approach, use Controller as approach. Or put the filterModelIsOpened in an object. The first approach is better.
<div ng-controller="SomeController as s">
<path-filter-modal is-opened="s.filterModalIsOpened">
</div>
function SomeController() { // no need to use $scope
this.filterModalIsOpened = false;
}
Or if you are using older version of Angular, you cannot use Controller as approach. Just create your own alias in the controller:
<div ng-controller="SomeController">
<path-filter-modal is-opened="s.filterModalIsOpened">
</div>
function SomeController($scope) {
$scope["s"] = this;
this.filterModalIsOpened = false;
}
Here's a good article explaining the prototypal inheritance: http://codetunnel.io/angularjs-controller-as-or-scope/
Here are the demo why you should always prefix your model, be they are object or primitive.
Not recommended. Live code demo: http://jsfiddle.net/hdks813z/1/
<div ng-app="App" ng-controller="Ctrl">
<div ng-if="true">
<input type="checkbox" ng-model="filterModalCanBeOpened"/>
<the-directive primitive-param="filterModalCanBeOpened"></the-directive>
</div>
<hr/>
<p>
The value below doesn't react to changes in primitive(non-object) property
that is created a copy on a directive(e.g., ng-repeat, ng-if) that creates
child scope
</p>
$scope.primitive: {{filterModalCanBeOpened}}
</div>
angular.module('App', [])
.directive('theDirective', function () {
return {
restrict: 'AE',
scope: {
primitiveParam: '='
},
template: '<div>primitiveParam from directive: {{ primitiveParam }}; </div>',
link: function (scope) {
}
};
})
.controller('Ctrl', ['$scope', function ($scope) {
$scope.filterModalCanBeOpened = true;
}]);
Recommended: Live code demo: http://jsfiddle.net/2rpv27kt/
<div ng-app="App" ng-controller="Ctrl as c">
<div ng-if="true">
<input type="checkbox" ng-model="c.filterModalCanBeOpened"/>
<the-directive primitive-param="c.filterModalCanBeOpened"></the-directive>
</div>
<hr/>
<p>
The value below react to changes in primitive(non-object) property that is
addressed directly by its alias c, creating child scope on it would be
impossible. So the primitive below react to changes on
the c's filterModalCanBeOpened.
</p>
c.primitive: {{c.filterModalCanBeOpened}}
</div>
angular.module('App', [])
.directive('theDirective', function () {
return {
restrict: 'AE',
scope: {
primitiveParam: '='
},
template: '<div>primitiveParam from directive: {{ primitiveParam }}; </div>',
link: function (scope) {
}
};
})
.controller('Ctrl', [function () {
this.filterModalCanBeOpened = true;
}]);