Make Custom Taxonomy Category Use Parent Template

Question

I have a Wordpress custom post type set up in my functions.php called "Research"

I have a custom taxonomy called "Classifications"

Under that taxonomy I have the terms/categories:

Old Research (parent) 
--- sub cat 1 
--- sub cat 2

I have created the file "taxonomy-Classifications-oldresearch.php" which successfully changes the parent layout for me. However, it does not hold the layout in the sub categories. The sub-category pages revert to another file taxonomy-Classifications.php

I can alter it by also creating taxonomy-Classifications-subcat1-oldresearch.php but I will have a lot of sub categories that I want to use ONE template for - the parent cat template. This way I don't have to create a new template file for every new category.

Answer 1

Hook into template_include filter

add_filter('template_include', 'research_term_template');

function research_term_template( $template ) {
  if ( is_tax('classifications') ) {
    $parent = get_term_by('slug', 'oldresearch', 'classifications');
    // to improve performance you can hardcoding 'oldresearch' term id
    // $parent = 12;
    if ( term_is_ancestor_of( $parent, get_queried_object(), 'classifications' ) )
       return get_template_directory() . '/taxonomy-Classifications-oldresearch.php';
  }
  return $template;
}

Answer 2

Change template file name taxonomy-Classifications-oldresearch.php to taxonomy-Classifications.php so that it will work for both parent and child terms of Classifications custom taxonomy.

Answer 3

In taxonomy-Classifications.php you can add some logic to check the term and then include a loop template specific to that term.

// seudo-code logic example
if Classifications,  
    use loop-classifactions.php  

else if Classifications -> Old Research,  
    use loop-classifications-oldresearch.php

else if Classifications -> Old Research -> Child Term,  
    use loop-classifications-oldresearch-child.php

I believe this is the solution you are after. Get template part based on custom taxonomy term

Answer 4

Reading the taxonomy templates hierarchy documentation seems like it is working as expected. The file taxonomy-Classifications-oldresearch.php is specific for oldresearch term and that file won't be used by any other term. The file taxonomy-Classifications.php will be used by all terms of Classifications taxonomy except by the terms with a specific template like taxonomy-Classifications-oldresearch.php.

The template taxonomy hierarchy is as follow:

1. A term-specific template is the first template used by Wordpress (in this case taxonomy-Classifications-oldresearch.php).
2. If no term-specific template is found, then wordpress will use taxonomy-spceific template (in this case taxonomy-Classifications.php).
3. If no taxonomy-specific template is found, then wordpress will use a general template for all taxonomies (taxonomy.php).
4. If taxonomy.php is not found, wordpress will use the archive.php template.
5. Finally, if archive.php is not found Wordpress will use index.php.

To alter this behaviour you can check the parent of the current term and use get_template_part() function or include/requiere to load the template you want. There is no other solution, I think. For example, in taxonomy-Classifications.php:

$term = get_term_by( 'slug', get_query_var('term'), 'Classifications' );
if($term->parent == 'your_oldresearch_term_ID'){
   inclue(get_template_directory().'/taxonomy-Classifications-oldresearch.php');
} else {
  .....
  .....
}