How to request container_class from wp_nav_menu

Question

I'm currently trying to setup a custom nav walker that will use container_class from the menu as a prefix for the class names of the list items and children.

$defaults = array(
'menu'            => '',
'menu_class'      => '',
'menu_id'     => '',
'container'       => 'nav',
'container_class' => 'nav-primary',
'container_id'    => '',
'before'      => '',
'after'       => '',
'link_before'     => '',
'link_after'      => '',
'depth'       => 0,
'walker'          => new Custom_Nav_Walker(),
'theme_location'  => 'primary',
'items_wrap'      => '<ul>%3$s</ul>',
);
wp_nav_menu( $defaults );

The general idea is the walker will loop out the classes according to the container class name. Like so.

<nav class="nav-primary">
  <li class="nav-primary__item"><a href="#">Link</a></li>
  <li class="nav-primary__item"><a href="#">Link</a></li>
  <li class="nav-primary__item"><a href="#">Link</a></li>
</nav>

Hopefully someone can help.

Answer 1

Go with a custom Walker

class Your_Walker_Nav_Menu extends Walker_Nav_Menu {
    var $container_class;
    public function __construct($container_class) {
        $this->container_class = $container_class;
    }

    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {
        global $wp_query;
        $indent = ( $depth > 0 ? str_repeat( "\t", $depth ) : '' ); // code indent

        // Depth-dependent classes.
        $depth_classes = array(
            ( $depth == 0 ? 'main-menu-item' : 'sub-menu-item' ),
            ( $depth >=2 ? 'sub-sub-menu-item' : '' ),
            ( $depth % 2 ? 'menu-item-odd' : 'menu-item-even' ),
            'menu-item-depth-' . $depth
        );
        $depth_class_names = esc_attr( implode( ' ', $depth_classes ) );

        // Passed classes.
        $classes = empty( $item->classes ) ? array() : (array) $item->classes;
        $class_names = esc_attr( implode( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item ) ) );

        // Build HTML.
        $output .= $indent . '<li id="nav-menu-item-'. $item->ID . '" class="'. $this->container_class . '__item ' . $depth_class_names . ' ' . $class_names . '">';

        // Link attributes.
        $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 .= ' class="menu-link ' . ( $depth > 0 ? 'sub-menu-link' : 'main-menu-link' ) . '"';

        // Build HTML output and pass through the proper filter.
        $item_output = sprintf( '%1$s<a%2$s>%3$s%4$s%5$s</a>%6$s',
            $args->before,
            $attributes,
            $args->link_before,
            apply_filters( 'the_title', $item->title, $item->ID ),
            $args->link_after,
            $args->after
        );
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );
    }
}

Notice the construct function, then when you call the menu:

'container_class' => 'nav-primary',
'walker' => new Your_Walker_Nav_Menu('nav-primary')

Answer 2

So far i've tried pulling the value from the nav template.

https://github.com/WordPress/WordPress/blob/master/wp-includes/nav-menu-template.php.

I know it's related to
$class = $args->container_class ? ' class="' . esc_attr( $args->container_class ) . '"' : ' class="menu-'. $menu->slug .'-container"'; on line 353.

The value returns null when requesting it. The idea is to loop the value out as part of the class name. As I only need to return the name itself.

'primary-menu__item'

would become

$container_class . '-menu__item