Secondary Menu and Logged In Users

Question

I'm using the below code to display two different menus in my storefront based child theme based on a users logged in status. But When I have a secondary menu (links by the search bar) it is replaced with the primary menu. Is there a way to differentiate between the two when checking for logged in users?

The below code is in my functions.php file.

//Custom Nav Menu
function custom_wp_nav_menu_args( $args = '' ) {
    if( is_user_logged_in() ) {
        $args['menu'] = 'logged-in';
    }else { 
        $args['menu'] = 'logged-out';
    } 
    return $args;
}
add_filter( 'wp_nav_menu_args', 'custom_wp_nav_menu_args' );

The theme is the default storefront theme, which should displays the secondary menu to the left of the search box. As you can see here its displaying (either) the logged-in or logged-out menu.

Please see Selected answer for more information. My Working Code...

//Custom Nav Menu
function custom_wp_nav_menu_args($args) {
    if ( isset($args['theme_location']) && 'primary' === $args['theme_location'] ) {
            // do something
        if( is_user_logged_in() ) {
            $args['menu'] = 'logged-in';
        }else { 
            $args['menu'] = 'logged-out';
        }
    } 
    return $args;
}
add_filter( 'wp_nav_menu_args', 'custom_wp_nav_menu_args' );

Answer 1

wp_nav_menu_args is a filter inside wp_nav_menu, which is used to display navigation menus on your site. The $args parameter passed to the filter is an array containing the wp_nav_menu arguments. By default they are the following,

$defaults = array(
  'menu'            => '',
  'container'       => 'div',
  'container_class' => '',
  'container_id'    => '',
  'menu_class'      => 'menu',
  'menu_id'         => '',
  'echo'            => true,
  'fallback_cb'     => 'wp_page_menu',
  'before'          => '',
  'after'           => '',
  'link_before'     => '',
  'link_after'      => '',
  'items_wrap'      => '<ul id="%1$s" class="%2$s">%3$s</ul>',
  'item_spacing'    => 'preserve',
  'depth'           => 0,
  'walker'          => '',
  'theme_location'  => '',
);

You can find these also in the wp_nav_menu code reference and in its source code. (These are merged with the theme supplied arguments by wp_parse_args before being passed to the wp_nav_menu_args filter.)

This means you can use the parameter to check for example which location the filter is currently handling.

add_filter('wp_nav_menu_args', 'my_wp_nav_menu_args_filter');
function my_wp_nav_menu_args_filter($args) {
  if ( isset($args['theme_location']) && 'my-theme-location' === $args['theme_location'] ) {
    // do something
  }
  return $args;
}

(For Storefront the location slug is secondary, which you can find in the source code.)