Make custom post column sortable

Question

I have a custom column listing a post_meta value for each post in the post list screen. I could only find information on how to make a custom post type sortable. How do I make this sortable? Thanks in advance.

add_filter('manage_posts_columns' , 'ws_add_manufacturer_column');
function ws_add_manufacturer_column($defaults){
    $defaults['manufacturer'] = 'Manufacturer';
    return $defaults;
}

add_action('manage_posts_custom_column', 'ws_add_manufacturer_content', 
10, 2);
function ws_add_manufacturer_content($column_name, $post_ID) {
    if ($column_name == 'manufacturer') {
    $manufacturer_name = get_post_meta( $post_ID, 'wccaf_manufacturer', 
true );
    if ($manufacturer_name) {
        echo $manufacturer_name;
    }
    }
}

Answer 1

You need two additional functions.

The first to make the column sortable hooks into the manage_edit-{post_type}_sortable_columns filter...

function ws_sortable_manufacturer_column( $columns )    {
    $columns['manufacturer'] = 'Manufacturer';
    return $columns;
}
add_filter( 'manage_edit-post_sortable_columns', 'ws_sortable_manufacturer_column' );

and the second hooks into pre_get_posts to manipulate the query to sort by the column...

function ws_orderby_custom_column( $query ) {
    global $pagenow;

    if ( ! is_admin() || 'edit.php' != $pagenow || ! $query->is_main_query() || 'post' != $query->get( 'post_type' ) )  {
        return;
    }

    $orderby = $query->get( 'orderby' );

    switch ( $orderby ) {
        case 'manufacturer':
            $query->set( 'meta_key', 'wccaf_manufacturer' );
            $query->set( 'orderby', 'meta_value' );
            break;

        default:
            break;
    }

}
add_action( 'pre_get_posts', 'ws_orderby_custom_column' );

Hope that helps