Get slug of current category in functions.php

Question

I want to use a certain archive template for a bunch of different parent categories. Therefor I try to change the archive template by using the 'archive_template' filter in functions.php by identifying what slug the current category has.

I've tried to retrieve the category slug by using three different methods as you can see below, but none of them seem to work. What's the correct way of retrieving the current category in functions.php?

function use_custom_template($tpl){
    global $post;

    $tryOne = get_the_category( $post->ID );    
    $tryTwo = get_the_category();
    $tryThree = get_queried_object();
      
  if (is_tax("sport-fritid-parent") {
    $tpl = dirname( __FILE__ ) . '/category-custom-parent.php';
  }
  return $tpl;
}

add_filter( 'archive_template', 'use_custom_template' ) ;

Answer 1

get_queried_object is how you retrieve the term for the current category, although you have to be careful to check for this, as it may not be a category archive. It could be a date archive, or a tag archive, etc etc

At a minimum you should include an is_category check:

https://developer.wordpress.org/reference/functions/is_category/

Reading the docs for is_category also reveals it takes a parameter so not only can you check if it's a category, you can use it to check if it's a specific category.

You should also look into using locate_template to grab the path to the file rather than dirname( __FILE__ ). This is because the current code has no support for child themes or plugin overrides.

see https://developer.wordpress.org/reference/functions/locate_template/

Another solution would have been to use category-sport-fritid-parent.php and then inside that file called get_template_part to pull in a shared template file.

For reference, here is the official documentation for the filter you're trying to use:

https://developer.wordpress.org/reference/hooks/type_template/

And post in the comments of that doc is an example doing exactly what you're asking how to do:

https://developer.wordpress.org/reference/hooks/type_template/#comment-4683