Custom post type structure for posts with multiple child posts

1 comment

1. I’ve waited for quite a while for an answer to this and have had to continue on with the project so thought I would answer myself

   First off I set up the custom post type of language, then hooked in to the publish_language action to programatically add child posts like so:

   function ta_insert_child_posts($post_id) {  
       if(($_POST['post_status'] == 'publish') && ($_POST['original_post_status'] != 'publish')) {
           $post = get_post($post_id);
   
           // Make sure it's a top level language being published
           if($post->post_parent == 0) {
               // Create our array of child post titles
               $child_posts = array('History', 'Where is it spoken', 'Also known as', 'Dialects', 'Alphabet & Writing System');
   
               foreach($child_posts as $child_post_title) {
                   // Insert each new post as a child of the new language
                   wp_insert_post(array(
                       'post_title' => $child_post_title,
                       'post_parent' => $post_id,
                       'post_type' => 'language',
                       'post_status' => $post->post_status 
                   ));
               }
           }
       }
   }
   add_action('publish_language', 'ta_insert_child_posts');
   

   Next, I had to add in logic to delete/trash child posts when their parent was deleted/trashed by hooking in to before_delete_post and trash_language

   function ta_delete_child_posts($post_id) {
       global $post_type;
   
       if($post_type != 'language') return;
   
       $child_posts = get_posts(array('post_parent' => $post_id, 'post_type' => 'language'));
   
       if(is_array($child_posts)) {
           foreach($child_posts as $child_post) {
               wp_delete_post($child_post->ID, true);
           }
       }
   }
   add_action('before_delete_post', 'ta_delete_child_posts');
   
   function ta_trash_child_posts($post_id) {
       $child_posts = get_posts(array('post_parent' => $post_id, 'post_type' => 'language'));
   
       if(is_array($child_posts)) {
           foreach($child_posts as $child_post) {
               wp_trash_post($child_post->ID);
           }
       }
   }
   add_action('trash_language', 'ta_trash_child_posts');
   

   Ok so we now have child posts being published and deleted in sync with their parent language. Next I had to ensure only top level languages were being pulled through in the admin ui language list so I hooked in to the request action:

   function ta_modify_request($request) {
       if(is_admin()) {
           $screen = get_current_screen();
   
           // We only want to retrieve top level language posts in the main request
           if($screen->post_type == 'language') {
              $request['post_parent'] = 0;
           }
       }
   
       return $request;
   }
   add_action('request', 'ta_modify_request');
   

   Lastly, I had to inject some custom CSS and JavaScript by hooking in to admin_footer which added an expand/contract link to each language, with an ajax call to a function which gets child posts of the selected language and displays them in the standard wordpress table format:

   function ta_child_posts_scripts() {
       $screen = get_current_screen();
   
       if($screen->post_type == 'language') {
   ?>
       <style type="text/css">
           #the-list tr .sorting-indicator {top:10px;position:relative;margin-top:0;cursor:pointer}
           #the-list tr .sorting-indicator.show:before {content:''}
           #the-list tr:hover .sorting-indicator {display:inline-block}
       </style>
       <script type="text/javascript">
           jQuery(function($) {
               $('#the-list tr .row-title').each(function() {
                   $(this).after('<span class="sorting-indicator show" title="Show Child Posts"></span>');
               });
   
               $('#the-list tr .sorting-indicator').on('click', function() {
                   var tr = $(this).parents('tr');
   
                   if($(this).hasClass('show')) {
                       var data = {
                           action: 'ta_child_posts',
                           post_id: tr.attr('id')
                       };
   
                       $.post(ajaxurl, data, function(response) {
                           $(response).hide().insertAfter(tr).fadeIn();
                       });
   
                       $(this).removeClass('show').addClass('hide');
   
                   } else {
                       tr.nextUntil('.level-0').fadeOut(function() { $(this).remove(); });
   
                       $(this).removeClass('hide').addClass('show');
                   }
               });           
   
           });
       </script>
   <?php
       }
   }
   
   add_action('admin_footer', 'ta_child_posts_scripts');
   

   With this in place, all I had left to do was the add in the ajax callback function to get the child posts based on the selected language:

   if(is_admin() && !class_exists('WP_List_Table')){
       require_once( ABSPATH . 'wp-admin/includes/class-wp-list-table.php' );
       require_once( ABSPATH . 'wp-admin/includes/class-wp-posts-list-table.php' );
   }
   
   function ta_get_child_posts() {
   
       if(empty($_POST['post_id'])) return;
   
       $post_id = explode('-', $_POST['post_id']);
   
       if(!isset($post_id[1])) return;
   
       $post_id = (int)$post_id[1];
   
       // Get child posts of the selected post
       $child_posts = get_posts(array('post_parent' => $post_id, 'post_type' => 'language'));
   
       set_current_screen('language');
   
       $ta_table = new WP_Posts_List_Table(array('screen' => get_current_screen()));
   
       $ta_table->prepare_items();
   
       // Since WP_List_Table provides no way to return its data we print the output with display_rows but catch it in an output buffer
       ob_start();
   
       $ta_table->display_rows($child_posts, 1);
       $rows = ob_get_clean();
   
       // Return the rows to the ajax callback
       die(print($rows));
   }
   
   add_action('wp_ajax_ta_child_posts', 'ta_get_child_posts');
   

   I hope this helps out a future googler with a similar issue or anyone else browsing this website

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