Monitoring $scope modifications within a directive: A simple guide

Question

Monitoring $scope modifications within a directive: A simple guide

I am currently working with a directive that looks like this:

app.directive('selectedForm', function(MainService) {
    return {
        scope: {
            formName: '=currentForm'
        },
        restrict: 'E', 
        link: function($scope, iElm, iAttrs, controller) {
            $scope.$watch('formName', function(oldV, newV) {
                console.log(iElm);
                if (someCondition) {
                    MainService.getForm($scope.formName).then(function(re) {
                        iElm.html(re);
                    });
                }
            });
        }
    };
});

Unfortunately, I have encountered an issue where I am unable to watch for changes. I have a <select> element in the DOM that updates the value of currentForm using ngModel. However, even after selecting an option, the watch function does not seem to work correctly. Am I overlooking something important here?

javascript angularjs angularjs-directive

Answer 1

Answer №1

When using the $watch function in an angular directive, it cannot be executed in the same manner as you would in an angular controller. To make it work, adjust your code to look like this:

Modify your html select element as follows:

<select model="selectedElements">
    ...
    ...
</select>

Within your directive, update the $watch section to:

...
link: function($scope, iElm, iAttrs, controller) {
            $scope.$watch('iAttrs.model', function(oldV, newV) {
...

For more information, check out this link: Is it ok watch the scope inside a custom directive?

EDIT:

To watch the value of

<select ng-model='currentForm'> ... </select>

, use the following code snippet:

...
link: function($scope, iElm, iAttrs, controller) {
            $scope.$watch('iAttrs.currentForm', function(oldV, newV) {
...

EDIT 2

Latest updates based on feedback received:

In your html

<selected-form ng-model="currentForm"></selectedForm>

and in your controller

...
link: function($scope, iElm, iAttrs, controller) {
            $scope.$watch('iAttrs.ngModel', function(oldV, newV) {
...

EDIT 3

Check out the updated plunker here:

https://plnkr.co/edit/v5EnmpQ9UtApnM5ErnYi?p=preview

Answer 2

When using the $watch function in an angular directive, it cannot be executed in the same manner as you would in an angular controller. To make it work, adjust your code to look like this:

Modify your html select element as follows:

<select model="selectedElements">
    ...
    ...
</select>

Within your directive, update the $watch section to:

...
link: function($scope, iElm, iAttrs, controller) {
            $scope.$watch('iAttrs.model', function(oldV, newV) {
...

For more information, check out this link: Is it ok watch the scope inside a custom directive?

EDIT:

To watch the value of

<select ng-model='currentForm'> ... </select>

, use the following code snippet:

...
link: function($scope, iElm, iAttrs, controller) {
            $scope.$watch('iAttrs.currentForm', function(oldV, newV) {
...

EDIT 2

Latest updates based on feedback received:

In your html

<selected-form ng-model="currentForm"></selectedForm>

and in your controller

...
link: function($scope, iElm, iAttrs, controller) {
            $scope.$watch('iAttrs.ngModel', function(oldV, newV) {
...

EDIT 3

Check out the updated plunker here:

https://plnkr.co/edit/v5EnmpQ9UtApnM5ErnYi?p=preview

Monitoring $scope modifications within a directive: A simple guide

Answer №1

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