How to request container_class from wp_nav_menu

Hi,

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.