Update parent scope variable

Problem

I have two controllers one wrapped within another. Now I know the child scope inherits properties from the parent scope but is there a way to update the parent scope variable? So far I have not come across any obvious solutions.

In my situation I have a calendar controller within a form. I would like to update the start and end dates from the parent scope (which is the form) so that the form has the start and end dates when submitted.

Problem courtesy of: Malcr001

Solution

You need to use an object (not a primitive) in the parent scope and then you will be able to update it directly from the child scope

Parent:

app.controller('ctrlParent',function($scope){
    $scope.parentprimitive = "someprimitive";
    $scope.parentobj = {};
    $scope.parentobj.parentproperty = "someproperty";
});

Child:

app.controller('ctrlChild',function($scope){
    $scope.parentprimitive = "this will NOT modify the parent"; //new child scope variable
    $scope.parentobj.parentproperty = "this WILL modify the parent";
});

Working demo: http://jsfiddle.net/sh0ber/xxNxj/

See What are the nuances of scope prototypal / prototypical inheritance in AngularJS?

Solution courtesy of: sh0ber

Discussion

For accessing variables declared in the parent, we should use $parent in child controller or template file

In controller

$scope.$parent.varaiable_name

In html template

ng-model="$parent.varaiable_name"
Discussion courtesy of: Nibu

There is one more way to do this task and to not use the $scope.$parent variable.

Just prepare a method for changing the value in parent scope and use it in child one. Like this:

app.controller('ctrlParent',function($scope) {
  $scope.simpleValue = 'x';
  $scope.changeSimpleValue = function(newVal) {
    $scope.simpleValue = newVal;
  };
});

app.controller('ctrlChild',function($scope){
    $scope.changeSimpleValue('y');
});

It also works and give you more control over the value changes.

You can then also call the method even in HTML like: <a ng-click="changeSimpleValue('y')" href="#">click me!</a>.

Discussion courtesy of: Ravbaker

This also works (but not sure whether this follows best practice or not)

app.controller('ctrlParent',function($scope) {
    $scope.simpleValue = 'x';
});

app.controller('ctrlChild',function($scope){
    $scope.$parent.simpleValue = 'y';
});
Discussion courtesy of: DynamicNate

When you assign a primitive attribute to a scope, it is always local to the scope (possibly created on the fly), even if a parent scope has an attribute with the same name. This is a design decision, and a good one IMHO.

If you need to change some primitive (ints, booleans, strings) in the parent scope, from the view, you need it to be an attribute of another object in that scope, so the assignment may read:

<a ng-click="viewData.myAttr = 4">Click me!</a>

and it will, in turn:

  1. get the viewData object from whatever scope it is defined in
  2. assign 4 to its myAttr attribute.
Discussion courtesy of: rewritten

This recipe can be found in it's original form on Stack Over Flow.