[Plugin: Posts 2 Posts] Exclusive relations (er, monogamy? ;-) )

Does anybody know if this is possible with the Posts 2 Posts plugin? Scribu?

It should be possible, but it will require a significant amount of custom code.

Do you think it’s a viable option to use your plugin for what I want to achieve? Or would it be a better option to custom code this from scratch?

Maybe I exagerated when I said “a significant amount”.

With the development version (0.8-beta), you just need to extend the P2P_Box_Multiple class and overwrite the get_query_vars() method:

https://github.com/scribu/wp-posts-to-posts/wiki/Custom-boxes

That’s a lot less code you have to write than starting from scratch.

You’re right, that was tough! ??

I did this, at first glance it seems to work. Is this what you were talking about?

class DGO_P2P_Box extends P2P_Box_Multiple {

		protected function get_query_vars( $post_id, $page, $search ) {
			$query_vars = parent::get_query_vars( $post_id, $page, $search );

			// We want to only be able to connect posts that have the 'foo' tag.
			$query_vars['connected_from'] = null;

			return $query_vars;
		}
	}

Oh wait, that actually doesn’t work. NVM.

So, this is how I ended up fixing it:

class My_P2P_Box extends P2P_Box_Multiple {

        protected function get_query_vars($post_id, $page, $search) {
            global $wpdb;

            $query_vars = parent::get_query_vars($post_id, $page, $search);

            $query = "SELECT $wpdb->p2p.p2p_to AS post_id FROM $wpdb->p2p";

            $results = $wpdb->get_results($query);

            $r = array();
            foreach ($results as $row)
                $r[] = $row->post_id;

            $query_vars['post__not_in'] = $r;
            $query_vars['orderby'] = 'date';
            $query_vars['order'] = 'ASC';

            return $query_vars;
        }

    }

    p2p_register_connection_type(array(
        'from' => 'post',
        'to' => 'other_post_type',
        'box' => 'My_P2P_Box'
    ));

For whoever is interested.

Glad to see you figured it out.

Note that you can replace this:

$results = $wpdb->get_results($query);

$r = array();
foreach ($results as $row)
    $r[] = $row->post_id;

with this:

$r = $wpdb->get_col($query);