Wordpress Post ID in wp_nav_menu? - php

Question

I'm looking to add the post ID to the markup of wp_nav_menu but not sure how to approach it.
I've found this: http://wordpress.org/support/topic/output-the-post-id-of-wp_nav_menu-items
which suggests this, but putting it in my functions.php file doesnt do any thing.
// get menu item's content id
class pages_from_nav extends Walker_Nav_Menu
{
function start_el(&$output, $item, $depth, $args)
{
global $wp_query;
$item_output .= $item->object_id;
$item_output .= ',';
$output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );
}
}
Any ideas on how I could get the post ID as either a class, an ID or a data attribute?

Answer 1

Have it figured out via some nice chaps on the WP forums.
Needed to create a walker, which is a custo nav structure:
// nav menu walker
class My_Walker extends Walker_Nav_Menu
{
function start_el(&$output, $item, $depth, $args) {
global $wp_query;
$indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';
$class_names = $value = '';
$classes = empty( $item->classes ) ? array() : (array) $item->classes;
$class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item ) );
$class_names = ' class="' . esc_attr( $class_names ) . '"';
$output .= $indent . '<li id="menu-item-'. $item->ID . '"' . $value . $class_names .'>';
$attributes = ! empty( $item->attr_title ) ? ' title="' . esc_attr( $item->attr_title ) .'"' : '';
$attributes .= ! empty( $item->target ) ? ' target="' . esc_attr( $item->target ) .'"' : '';
$attributes .= ! empty( $item->xfn ) ? ' rel="' . esc_attr( $item->xfn ) .'"' : '';
$attributes .= ! empty( $item->url ) ? ' href="' . esc_attr( $item->url ) .'"' : '';
$attributes .= ' data-id="'. esc_attr( $item->object_id ) .'"';
$attributes .= ' data-slug="'. esc_attr( basename(get_permalink($item->object_id )) ) .'"';
$item_output = $args->before;
$item_output .= '<a'. $attributes .'>';
$item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;
$item_output .= '</a>'; /* This is where I changed things. */
$item_output .= $args->after;
$output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );
}
}
Then just pass the walker into my menu when I call wp_nav_menu();
<?php
$walker = new My_Walker;
wp_nav_menu(array(
'echo' => true,
'menu' => 4,
'container' => '',
'theme_location' => 'primary',
'menu_class' => 'grid-10 omega',
'walker' => $walker
)); ?>

Answer 2

Seems like this was over complicated. All you really need is url_to_postid(); where the URL you pass will be the link for the menu item.
add_filter('nav_menu_link_attributes', 'menu_post_ids');
function menu_post_ids($val){
$postid = url_to_postid( $val['href'] );
$val['data-postid'] = $postid;
return $val;
}
You could also use this to query data from the post such as a featured image, etc., and further manipulate the menu on the front end using jQuery and whatever post related attributes you added.
add_filter('nav_menu_link_attributes', 'my_menu_images');
function my_menu_images($val){
$postid = url_to_postid( $val['href'] );
$val['data-image'] = get_the_post_thumbnail_url($postid);
return $val;
}