Bootstrap Modal with AngularJS

We’ll look at a relatively low hanging fruit in case you’re working with vanilla AngularJS and Twitter Bootstrap and are not relying on other add-ons such as AngularUI’s Bootstrap extension. One common need I have is to be able to show or hide Bootstrap modals based on a property on my view-model. Here’s a simplified view of the controller:

var app = angular.module('app', ...);
...

app.controller('ctrl', function ($scope, ...) {
    ...
    $scope.showModal = false;
    ...
});

And here is the HTML:

<a href="#myModal" data-toggle="modal">Show Modal</a>
...
...
<div id="myModal" data-backdrop="static">
    <div>
        Modal text goes here.
        <br/>
        <button data-dismiss="modal">Close</button>
    </div>
</div>

In order to maintain separation of concerns, I want to be able to show or hide the modal as the value of showModal changes. This is another good use for directives in AngularJS. As with the datepicker example, we need a directive that will add a watch on link and use the JavaScript methods available with Bootstrap to control the modal, rather than the data-toggle or data-dismiss attributes.

The directive would then look like:

app.directive('akModal', function() {
    return {
        restrict: 'A',
        link: function(scope, element, attrs) {
            scope.$watch(attrs.akModal, function(value) {
                if (value) element.modal('show');
                else element.modal('hide');
            });
        }
    };
});

Here, we are calling the Boostrap method modal on the element to which the directive is applied, i.e. the div that is the modal container. The HTML modified to work with this directive then looks like:

<a href="#" ng-click="showModal = true">Show Modal</a>
...
...
<div ak-modal="showModal" data-backdrop="static">
    <div>
        Modal text goes here.
        <br/>
        <button ng-click="showModal = false">Close</button>
    </div>
</div>

The modal display is now bound to showModal. Note how we got rid of data-toggle (along with the id on the div) and data-dismiss. Now, if some property on the view-model needs to control whether the modal is displayed, then it would not make sense to have a link hardwired to trigger the specific modal anyway. The case for data-dismiss is different though.

Another thing to consider is – if you have a lot of modals and a lot of different view-model properties controlling them, you are going to have a lot of watches, which you probably don’t want. If we make the assumption that mostly you’re going to have one modal visible at a time (unless you have multiple levels of modals going on – in which case personally I think you would need to rethink the UX you are providing), you can make something more generic such as a modalService that will work with a single modal div and have a showModal operation that takes the content to display in the modal. There would need to be a corresponding hideModal operation as well, of course. I plan to explore this further.

Now, back to the data-dismiss thing. What we have at the moment is somewhat of a one-way binding. It would be ideal if this could be made two-way so that closing the modal using data-dismiss automatically set showModal to false. At the moment, I have not given this enough effort to be able to do it in an acceptably performant way. If someone has, I would love to hear about it.