How to use `str::slug`

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3

(Sorry)
I had time to try this out only today.

I am trying to sluggify a foreach loop outputting tags.

I tried to simplify and adjust the code from this post to my needs, but it’s not working.

In blog.php's controller I have:

return function($site, $pages, $page) {

  // get all articles
  $articles = $page->children()->visible()->flip();

  // fetch all tags
  $topics = $articles->pluck('topics', ',', false);

  //add tag filter (`topic`)
  if(!empty(param('topics'))) {
    $topics = str::slug(param('topics'));
    $articles = $articles->filter(function($article) use($topics) {
      // split tags and convert to lowercase
      $topics = array_map('str::slug', $article->topics()->split(','));
    });
  }
  return compact('articles', 'topics', 'topic');

};

and in the blog.php template:

<?php foreach($topics as $topic): ?>
  <div class="c-tag-collection__tag-name filter" data-filter=".<?php echo html($topic) ?>">
	<?php echo html($topic) ?>
  </div>
<?php endforeach ?>

Is it better to add slug:: in the controller or directly in the template?
What am I doing wrong?