The isolate scope variable is becoming undefined within the link function

When working with a directive that takes a data object and a function in its isolate scope, I encountered an issue. Inside the link function, I declared a method to be triggered on a button click event.

The problem is that while the value passed to the method works fine, the scope variable remains undefined.

Directive:

commentsModule.directive('commentsDirective', [ function() {
        return {
            restrict: 'E',
            templateUrl: '/alarm-viewer-comments-template.html',
            scope: {
                alarmComments: "=value",
                sendNewComment: "&sendNewComment"
            },
            link: function(scope, elems, attrs, ngModelCtrl) {
                scope.sendComment = function(data) {
                    console.log(scope.newComment);//this newComment variable is undefined
                    scope.sendNewComment(data);//data is correct
                    scope.newComment = '';
                };
            }
        }
    }
]);

Within the link function, the data passed into scope.sendComment is accessible, but scope.newComment remains undefined. Template:

<h4>Comments</h4>
<div ng-repeat="comment in alarmComments.comments">
    <p>{{comment.timestamp}} | <strong>{{comment.user}}</strong>: {{comment.commentType}} {{comment.comment}}</p>
</div>
<div ng-if="alarmComments.editPermission && alarmComments.isActiveAlarm">
    <form name="commentsForm" role="form"  track-form>
        <input type="text" ng-model="newComment" pattern="/.{1,}" maxlength="4" required ng-enter="sendComment(newComment)"/>
        <button type="button" class="btn btn-primary" ng-disabled="commentsForm.$invalid" ng-click="sendComment(newComment)">Send</button>
    </form>
</div>

UI:

<comments-directive value="alarmComments" send-new-comment="addNewComment(comment)"></comments-directive>

Any help or suggestions would be greatly appreciated!

edit: I am looking to clear the input text field after entering a comment.

Answer №1

To properly define the scope within a directive, it's important to include both the newComment and alarmComments properties as shown below:

scope: {
    alarmComments: "=value",
    newComment: "=newComment",
    sendNewComment: "&sendNewComment"
},

Answer №2

One effective method for troubleshooting issues like this is to display the scope ids (scope.$id) and ensure they match.

Have you checked the scope.$id during the linking process and displayed it in your template?

<h4>Comments</h4>
<div ng-repeat="comment in alarmComments.comments">
<p>{{comment.timestamp}} | <strong>{{comment.user}}</strong>:   {{comment.commentType}} {{comment.comment}}</p>
</div>
 <div ng-if="alarmComments.editPermission && alarmComments.isActiveAlarm">
<form name="commentsForm" role="form"  track-form>
    <input type="text" ng-model="newComment" pattern="/.{1,}" maxlength="4" required ng-enter="sendComment(newComment)"/>
    <button type="button" class="btn btn-primary" ng-disabled="commentsForm.$invalid" ng-click="sendComment(newComment)">Send</button>
{{$id}}
</form>
</div>

Sometimes templates generate their own scopes, requiring the use of $parent.newComment in your templates.

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