How do I list the tag groups that are actually in use?

Question

I'm developing a masonry photo gallery with some filters (colors, style, manufacturer, etc) and I want to use tags to filter them by. I need some navigation which should look like this:

<ul>
    <li>Tag Group 1
        <ul>
            <li>Tag 1</li>
            <li>Tag 2</li>
        </ul>
    </li>
    <li>Tag Group 2
        <ul>
            <li>Tag 3</li>
            <li>tag 4</li>
        </ul>
    </li>
</ul>

I read this article https://craftcms.com/support/active-tags but I can't figure out how to get all group tags and for them all the tags that are actualy in use. I think i should use

{% for tag in craft.tags.group('blogTags') %}

but I want to get all the group handles in a loop dynamically.

Answer 1

You could use the group filter to group your tags by tag groups:

{% set entries = craft.entries.section('gallery').limit(null) %}

<ul>

    {# Get all the tags related to our gallery entries and group them by tag group #}
    {% set allGalleryTags = craft.tags.relatedTo(entries)|group('group') %}

    {# Loop the tag groups #}
    {% for tagGroup, tagsInGroup in allGalleryTags %}

        <li>
            <h2>{{ tagGroup }}</h2>
            <ul>

                {# Loop the tags of this group #}
                {% for tag in tagsInGroup %}
                    <li>{{ tag.name }}</li>
                {% endfor %}

            </ul>
        </li>

    {% endfor %}

</ul>