Symfony/Twig - styling form widgets

Question

I'm trying to make an ugly file upload button look like a nice font awesome icon.

Here is what I have so far:

<div class="col-12 col-md-4">
    <button type="button" class="btn btn-round mt-0 mb-0 uploadMediaTrigger" data-toggle="modal" data-target="#uploadMedia" rel="tooltip" data-placement="top" title="Upload Media">
        <i class="far fa-images"></i>
    </button>
    {{ form_widget(postForm.file, { 'attr': {'class': 'far fa-images'} } ) }}
</div>

Do you know how I can get the ugly button to look like the font awesome icon? Seems like merely adding the font awesome classes doesn't work.

Here is a picture:

Answer 1

Check this answer with Form Themes and Form Extensions. This solution is compatible with Symfony 2.8.x and 4.x.

Can I put html inside a Symfony form button with Twig?