javascript - Angular Directive: Adding ng-class directive at compile time on existing template element - Stack Overflow

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Long story short, the idea is to simplify templating by not having to manually add ng-class={'has-error': 'formName.inputName.$invalid'} on every single form-group

So I want to create a directive that will generate a string that will be added to a template element. That string is an ng-class attribute with an expression

I thought that creating a quick directive that adds the ng-class attribute during the pile phase would be enough, but it doesn't seem to cut it.

Directive Definition Object

{
    restrict: 'C',
    pile: function(tElement, tAttrs) {
        var $elem = angular.element(tElement),
            formName = $elem.parents('[ng-form]').length ? $elem.parents('[ng-form]').attr('ng-form') : $elem.parents('form').attr('name'),
            controlName = $elem.find('.form-control').attr('name');

        $elem.attr('ng-class', '{"has-error": ' + formName + '.' + controlName + '.$invalid}');

        console.log('added ng-class attr', $elem.attr('ng-class'));
    }
}

Plunk here

See the console

The 1st form-group has its ng-class attribute added dynamically.
The expression associated with it is correct
But the ng-class directive is never executed

The 2nd form-group has its ng-class attribute added manually in the template and works as expected, obvisouly

--

What am I missing here?

Long story short, the idea is to simplify templating by not having to manually add ng-class={'has-error': 'formName.inputName.$invalid'} on every single form-group

So I want to create a directive that will generate a string that will be added to a template element. That string is an ng-class attribute with an expression

I thought that creating a quick directive that adds the ng-class attribute during the pile phase would be enough, but it doesn't seem to cut it.

Directive Definition Object

{
    restrict: 'C',
    pile: function(tElement, tAttrs) {
        var $elem = angular.element(tElement),
            formName = $elem.parents('[ng-form]').length ? $elem.parents('[ng-form]').attr('ng-form') : $elem.parents('form').attr('name'),
            controlName = $elem.find('.form-control').attr('name');

        $elem.attr('ng-class', '{"has-error": ' + formName + '.' + controlName + '.$invalid}');

        console.log('added ng-class attr', $elem.attr('ng-class'));
    }
}

Plunk here

See the console

The 1st form-group has its ng-class attribute added dynamically.
The expression associated with it is correct
But the ng-class directive is never executed

The 2nd form-group has its ng-class attribute added manually in the template and works as expected, obvisouly

--

What am I missing here?

• javascript
• angularjs
• angularjs-directive

Share Improve this question Follow edited Dec 3, 2015 at 21:58 Olivier Clément asked Dec 3, 2015 at 21:12 Olivier ClémentOlivier Clément 76411 gold badge99 silver badges2727 bronze badges

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2 Answers 2

Sorted by: Reset to default 6

Managed to make it work without adding extra watchers (granted, ng-class uses a watcher, but after testing the proposed solution I saw an increase in watchers amount)

I had to $pile the new DOM element in postLink, but to avoid recursion I need to remove the directive itself. This prevents me to reuse a class-name such as "form-group"

Here's the working Directive

function bsFormClass($pile) {
  return {
    restrict: 'A',

    pile: function (tElement) {

        var $elem = angular.element(tElement),
            controlName = $elem.find('.form-control').attr('name');

        if(!controlName) { return; }

        var formName = $elem.parents('[ng-form]').length ? $elem.parents('[ng-form]').attr('ng-form') : $elem.parents('form').attr('name');

        $elem.attr('ng-class', '{"has-error": ' + formName + '.' + controlName + '.$invalid}');
        $elem.removeAttr('bs-form-class');

        return {
            post: function(scope, elem, attrs) {
                $pile(elem)(scope);
            }
        }
    }
  }
}

Thanks for you help all

You cannot add directives to the current element!

In your case the solution is easy though; just watch the appropriate expressions and add the class as necessary:

function formGroupClass () {
    return {
        restrict: 'C',
        link: function(scope, elem, attrs) {
            var formName = elem.parents('[ng-form]').length ? elem.parents('[ng-form]').attr('ng-form') : elem.parents('form').attr('name'),
                controlName = elem.find('.form-control').attr('name');

            scope.$watch(formName + '.' + controlName + '.$invalid', function(newval) {
              elem.toggleClass('has-error', !!newval);
            });
        }
    };
}

The ng-class would add a watch anyway... See forked plunk: http://plnkr.co/edit/oKa6CKFoF1T5WoDzIPkI?p=preview

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