404 Issue w/ Custom Post Type - using Meta for Permalink rewrite

Question

I'm trying to rewrite my permalinks using meta data from my post. The permalink rewrite works- but I'm getting the 404 issue when I try to view the post.

I've flushed by visiting the permalink settings page, and still no dice.

Could someone offer a clue as to why this wouldn't work?

add_filter('post_type_link','calendar_link_filter',1,3);

function calendar_link_filter( $post_link, $id = 0, $leavename = FALSE ) {
    $post = get_post($id);
    if($post->post_type != 'super_duper') {
            return $post_link;
    }
    $date = get_post_meta($post->ID,'event_start_date',true);
    $date = strtotime($date);
    $str = $post_link;
    $str = str_replace('%cal_year%',date("Y",$date),$str);
    $str = str_replace('%cal_month%',date("m",$date),$str);
    $str = str_replace('%cal_day%',date("d",$date),$str);
    return $str;

}


add_action( 'init', 'create_my_post_types' );

function create_my_post_types() {
register_post_type( 'super_duper',
    array(
        'labels' => array(
            'name' => __( 'Super Dupers' ),
            'singular_name' => __( 'Super Duper' )
        ),
        'hierarchical' => false,
        'show_ui' => true, // UI in admin panel
        'publicly_queryable' => true,
        'rewrite' => true,
        'public' => true,
        'rewrite' => array('slug' => 'events8/%cal_year%/%cal_month%/%cal_day%'),


    )
);
flush_rewrite_rules();
}

Answer 1

Indeed, you need to add the rewrite tags. They indicate what can come in the place of your %cal_year% and similar tags:

add_rewrite_tag( '%cal_year%', '([0-9]{4})' );
add_rewrite_tag( '%cal_month%', '([0-9]{1,2})' );
add_rewrite_tag( '%cal_day%', '([0-9]{1,2})' );

This works, but I don't understand how: it seems to me something is missing to let WordPress know how it should get from 2010/12/31 to 2010-12-31 or however you saved your custom value. Maybe it just defaults back to the slug?