Best way to organize book-page structure

1 comment

1. I don’t know if this is the optimal, it’s one suggestion.

   For me I’d created the qa post type as hierachical.

   Then for every page in the book I’d created a child qa post using menu_order field to handle the page number.

   This child has a 3rd level child for problems.

   Hooking intro pre_get_posts for qa archive, you can set the post_parent to 0, so in the archive view you get only books, and not the big list of pages and problems.

   Last thing to is create a rewrite rule that convert the url into some query vars.

   E.g.

   <domain>/qa/<book-name>/<page-number>/<problem-number> should be rewritten in

    <domain>/index.php?name=<book-name>&post_type=qa&number=<page-number>&problem=<problem-number>
   

   That url will end in a very simple query where post id = <problem-number>.

   Example code:

   function my_book_rules() {
     add_rewrite_rule( 'qa/([^/]+)/([0-9]+)/([0-9]+)$', 'index.php?&post_type=qa&name=$matches[1]&number=$matches[2]&problem=$matches[3]', 'top' );
     add_rewrite_rule( 'qa/([^/]+)/([0-9]+)$', 'index.php?&post_type=qa&name=$matches[1]&number=$matches[2]', 'top');
   }
   add_action('init', 'my_book_rules');
   
   function my_book_query_vars($vars) {
     $vars[] = 'problem';
     $vars[] = 'number';   
     return $vars;
   }
   
   add_filter('query_vars', 'my_book_query_vars'); 
   
   function my_book_query( $query ) {
     if ( is_admin() || ! is_main_query() ) return;
     if ( is_archive() && $query->get('post_type') == 'qa') {
        $query->set('post_parent', 0);
     } elseif ( is_single() && get_post_type() == 'qa') {
       $post = get_queried_object();
       if ( $post->post_parent == 0 && $query->get('number') && ! $query->get('problem') ) {
         // a page number is requested
         $query->set('name', '');
         global $wpdb;
         $n = intval($query->get('number'));
         $p = (int) $wpdb->get_var("SELECT ID FROM $wpdb->posts WHERE post_status = 'publish' AND post_type = 'qa' AND post_parent = $post->ID AND menu_order = $n");
         $query->set('p', $n);
       } elseif( $query->get('problem') ) {
         // a problem is required
         $query->set('name', '');
         $n = intval($query->get('problem'));
         $query->set('p', $n);
       }
     }
   }
   add_action('pre_get_posts', 'my_book_query');
   

   In the single view template single-qa.php you can load sub tempalte for books, pages or problems, something like:

   if ( $post->post_parent == 0 ) {
      get_template_part('book', 'content');
   } else {
     $parent = get_post( $post->post_parent );
     if ( $parent->post_parent == 0 ) {
       get_template_part('page-number', 'content');
     } else {
       get_template_part('problem', 'content');
     }
   }
   

   Another snippet is for display the book title and the page number inside the problem template (problem-content.php according to previous snippet),

   $thepage = get_post( $post->post_parent);
   $pagenumber = $thepage->menu_order
   $the_book = get_post( $thepage->post_parent )->post_title
   
   echo "The problem " . get_the_title() . 
     " is in the book " . $the_book->post_title .
     " at the page number " . $pagenumber;
   

   Note that the code is a proof of concept and untested.

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