Reply To: Ordering by custom field of relationship field object

• drm10014

• August 22, 2018 at 4:25 pm

Meanwhile, I’ve converted the Relationship field to a Post Object field since each Artwork only has one Artist associated with it. That has this post object query filter:

function artist_post_object_query( $args, $field, $post_id ) {
$args['meta_query'] = array(
    'relation' => 'AND',
    'last_name' => array(
        'key' => 'artist_last_name'
	),
     'first_name' => array(
	'key' => 'artist_first_name'
      ));
      $args['orderby']	= array(
	'last_name' => 'ASC',
	'first_name' => 'ASC'
	);	
    // return
    return $args;
}
add_filter('acf/fields/post_object/query/name=artists_name', 'artist_post_object_query', 10, 3);

So Artist correctly alphabetized in the Artwork edit screen. (Although that filter doesn’t extend to the List screen sort order, for which I’m using Admin Columns Pro.)

Essentially I want that filter to work any time the Artworks field ‘artist_name’ is being used as a meta_key to sort so that ‘meta_value’ can be replaced with ‘artist_last_name’ + ‘artist_first_name’ instead of the post ID. It seems like a posts_join and then posts_orderby filter would work but I can’t get this join to work:

add_filter('posts_join', 'artist_join', 10, 2 );
function artist_join($joins)
{
    if(is_post_type_archive('artworks') || (is_admin() && $_GET['post_type'] == 'artworks')) {
        global $wpdb;        
        $joins .= "  INNER JOIN {$wpdb->postmeta} pm_last_name ON pm_last_name.post_id={$wpdb->posts}.ID
       WHERE pm_last_name.meta_key='artist_last_name'" ;
        $joins .= "  INNER JOIN {$wpdb->postmeta} pm_first_name ON pm_first_name.post_id={$wpdb->posts}.ID
       WHERE pm_first_name.meta_key='artist_first_name'" ;
    }
    return $joins;
}

Any help would be much appreciated.