Make *ALL* Wordpress Categories use their Parent Category Template

Question

I want to change the default template hierarchy behavior, and force all subcategory level pages that don't have their own category template file to refer to their parent category template file. In my other post, Richard M. gave an excellent answer that solved the problem for an individual subcategory. Does anyone know how to abstract it?

function myTemplateSelect()
{
    if (is_category()) {
        if (is_category(get_cat_id('projects')) || cat_is_ancestor_of(get_cat_id('projects'), get_query_var('cat'))) {
            load_template(TEMPLATEPATH . '/category-projects.php');
            exit;
        }
    }
}

add_action('template_redirect', 'myTemplateSelect');

Thanks in advance.

Answer 1

/**
 * Iterate up current category hierarchy until a template is found.
 * 
 * @link http://stackoverflow.com/a/3120150/247223
 */ 
function so_3119961_load_cat_parent_template( $template ) {
    if ( basename( $template ) === 'category.php' ) { // No custom template for this specific term, let's find it's parent
        $term = get_queried_object();

        while ( $term->parent ) {
            $term = get_category( $term->parent );

            if ( ! $term || is_wp_error( $term ) )
                break; // No valid parent

            if ( $_template = locate_template( "category-{$term->slug}.php" ) ) {
                // Found ya! Let's override $template and get outta here
                $template = $_template;
                break;
            }
        }
    }

    return $template;
}

add_filter( 'category_template', 'so_3119961_load_cat_parent_template' );

This loops up the parent hierarchy until an immediate template is found.