Assign Page Template Within A Custom Post Type

Question

I have registered a Custom Post Type and created a file called archive-myCPT.php and another one for single posts called single-myCPT.php.

What I want to do is to create a page where I will show just few posts from my Custom Post Type. Inside my archive-myCPT.php I will have a link called let's say "Special Posts" and this link will go to the custom page which will be a little bit different from archive-myCPT.php, the only difference is that here I will use a custom query for the posts.

The only way to do this seems to create a page template, but the problem here is that I can not assign a page template to pages within my CPT. I found this plugin which may help me with the page template support for my Custom Post Type, but is pretty old and I don't know if it's compatible with the latest version of WordPress.

Is there any other way to achieve this?

Is this a common / good practice?

Maybe you could recommend something else?

Answer 1

If you're adding a custom query within the template to load posts, the post type of that page doesn't have to be your custom post type. You can create a plain vanilla page, create a template for that via page-your_page_slug.php, or via a custom template assigned in the templates dropdown, then query for whatever post type you want via WP_Query.

EDIT - here's an example using the single_template filter. you'll have to change the post type and slug to match yours.

function wpa_single_cpt_template( $templates = '' ){
    $single = get_queried_object();

    if( 'myCPT' == $single->post_type
        && 'my-special-slug' == $single->post_name )
        $templates = locate_template( 'my-special-template.php', false );

    return $templates;
}
add_filter( 'single_template', 'wpa_single_cpt_template' );

adapted from the example on Template Hierarchy: Filter Hierarchy.

Answer 2

You would think that it would be as simple as adding add_post_type_support( 'cptslug', 'page-attributes' ); to your code, but it isn't. If you check the source you will see that the template dropdown is restricted to the page post type only. There is also a note in the Codex and a reference to a closed Trac ticket on the topic.

You can add that box to your CPT by copying the Core function, making a small edit and adding a new box.

function my_cpt_attributes_meta_box($post) {
    $post_type_object = get_post_type_object($post->post_type);
    if ( $post_type_object->hierarchical ) {
        $dropdown_args = array(
            'post_type'        => $post->post_type,
            'exclude_tree'     => $post->ID,
            'selected'         => $post->post_parent,
            'name'             => 'parent_id',
            'show_option_none' => __('(no parent)'),
            'sort_column'      => 'menu_order, post_title',
            'echo'             => 0,
        );

        $dropdown_args = apply_filters( 'page_attributes_dropdown_pages_args', $dropdown_args, $post );
        $pages = wp_dropdown_pages( $dropdown_args );
        if ( ! empty($pages) ) {
?>
<p><strong><?php _e('Parent') ?></strong></p>
<label class="screen-reader-text" for="parent_id"><?php _e('Parent') ?></label>
<?php echo $pages; ?>
<?php
        } // end empty pages check
    } // end hierarchical check.

        $template = get_post_meta($post->ID,'_wp_page_template',true);

        ?>
<p><strong><?php _e('Template') ?></strong></p>
<label class="screen-reader-text" for="page_template"><?php _e('Page Template') ?></label><select name="page_template" id="page_template">
<option value='default'><?php _e('Default Template'); ?></option>
<?php page_template_dropdown($template); ?>
</select>

<p><strong><?php _e('Order') ?></strong></p>
<p><label class="screen-reader-text" for="menu_order"><?php _e('Order') ?></label><input name="menu_order" type="text" size="4" id="menu_order" value="<?php echo esc_attr($post->menu_order) ?>" /></p>
<p><?php if ( 'page' == $post->post_type ) _e( 'Need help? Use the Help tab in the upper right of your screen.' ); ?></p>
<?php
}
function add_my_cpt_attributes_meta_box() {
  add_meta_box(
    'my_cpt_attributes_meta_box',
    'My Box Name',
    'my_cpt_attributes_meta_box',
    'book',
    'side',
    'core'
  );
}
add_action( 'add_meta_boxes', 'add_my_cpt_attributes_meta_box' );

If you test that code, you will notice that the box appears but the data doesn't save. Here is why.

We are going to have to save the data ourselves.

function my_save_cpt_template($post_ID,$post) {
  $page_template = (isset($_POST['page_template'])) ? $_POST['page_template'] : false;
  $page_templates = wp_get_theme()->get_page_templates();
//   var_dump($page_template,$page_templates,'default' != $page_template && ! isset( $page_templates[ $page_template ] )); die;
  if ( 'default' != $page_template && ! isset( $page_templates[ $page_template ] ) ) {
      if ( $wp_error )
          return new WP_Error('invalid_page_template', __('The page template is invalid.'));
      else
          return 0;
  }
  update_post_meta($post_ID, '_wp_page_template',  $page_template);
}
add_action('save_post_cptslug','my_save_cpt_template',1,2);

Now it should save but the template doesn't load. Here is why. get_single_template runs before get_page_template, and get_page_template is what looks for the specialized templates. So we need to load that template ourselves.

add_action(
  'template_include',
  function ($template) {
    global $post;
    if (is_singular() && isset($post->post_type) && 'book' === $post->post_type) {
      $new = get_post_meta($post->ID,'_wp_page_template',true);
      $new = locate_template($new);
      if (!empty($new)) {
        $template = $new;
      }
    }
    return $template;
  }
);

Barely tested. Possibly buggy. Caveat emptor. No refunds.