Is there a way to get supportedSites for a category page?

Question

I'm working on a site that is available in multiple languages and I would like to build a language switcher that will work for both category pages and single entries.

In Craft v2 that was possible but once I switched to Craft v3, I can't find a way to do get the current category page.

For single entries I do the following (simplified):

{% for siteForEntry in entry.getSupportedSites %}       
    {% set site = craft.app.getSites.getSiteById(siteForEntry.siteId) %}        
    {% if site.id == entry.siteId %}
        <li class="language-selection--active-language">
           <a href="#">{{ site.language }} </a> 
        </li>
    {% else %}            
        {% set entryForOtherSite = craft.entries.id(entry.id).site(site).one() %}
            <li class="{% if site.id == entry.siteId %} language-selection--active-language{% endif %} ">
                <a href="{{ entryForOtherSite.getUrl() }}">{{ site.language }} </a>
             </li>
        {% endif %}
 {% endfor %}

Is there a way to do the same thing for categories?

Answer 1

It turns out that getSupportedSites() returns different results for categories and standard entries so an additional check needs to take place.

The solution below has been tested with a single group with multiple languages, and it works, although I hope there's a better solution than this one:

If the current page is a category then assign it to the entry variable

{% set entry = category %}

Then:

{# Retrieve all supported sites for the current entry #}
{% set supportedSites = entry.getSupportedSites %}

<ul>
{% for siteForEntry in supportedSites %}
  {% if siteForEntry | length == 1 %}
    {# category #}
    {% set site = craft.app.getSites.getSiteById(siteForEntry) %}
    {% set entryForOtherSite = craft.categories.id(entry.id).site(site).one() %}
  {% elseif siteForEntry | length == 2 %}
    {# standard entry #}
    {% set site = craft.app.getSites.getSiteById(siteForEntry.siteId) %}
    {% set entryForOtherSite = craft.entries.id(entry.id).site(site).one() %}
  {% endif %}

  {% if site.id == entry.siteId %}
      {# This is the current language, mark it as active and don't retrieve its url #}
      <li class="current"><a href="#">{{site.language}}</a></li>
  {% else %}
      {# if it's not the current site, get the entry for this site #}
      <li><a href="{{ entryForOtherSite.getUrl() }}">{{site.language}}</a</li>
  {% endif %}

{% endfor %}
</ul>