How to override this theme function in child theme

Question

I'm working in a child theme and I need to override a function in order to remove some unwanted items on a top menu. So I have research a bit and found a lot of docs, really, like this, this and this among others but still not clear at all to me how to achieve this on my specific case. So I hope someone here can point me on the right direction. I have this functions at original theme functions.php file:

function udesign_nav() {
    if ( function_exists( 'wp_nav_menu' ) ) {
        $defaults = array(
            'container_class' => 'navigation-menu',
            'container_id' => 'navigation-menu',
            'menu_id'    => 'main-top-menu',
            'menu_class' => 'sf-menu',
            'link_before'=> '<span>',
            'link_after' => '</span>',
            'theme_location' => 'primary',
            'fallback_cb' => 'udesign_nav_fallback'
        );
        wp_nav_menu( $defaults );
    } else {
        udesign_nav_fallback();
    }
}

function udesign_nav_fallback() {
    $menu_html = '<div id="navigation-menu" class="navigation-menu">';
    $menu_html .= '<ul id="main-top-menu" class="sf-menu">';
    $menu_html .= is_front_page() ? "<li class='current_page_item'>" : "<li>";
    $menu_html .= '<a href="'.home_url().'"><span>'.esc_html__('Home', 'udesign').'</span></a></li>';
    $menu_html .= wp_list_pages('depth=5&title_li=0&sort_column=menu_order&link_before=<span>&link_after=</span>&echo=0');
    $menu_html .= '</ul>';
    $menu_html .= '</div>';
    echo $menu_html;
}

And it is called, I think, here:

// Setup the main menu
function udesign_top_main_menu() {
    ob_start(); ?>
            <div class="clear"></div>
            <div id="main-menu">
                <div id="dropdown-holder" class="container_24">
<?php               udesign_nav(); // this function calls the main menu ?>
                </div>
                <!-- end dropdown-holder -->
            </div>
            <!-- end top-main-menu -->
<?php
    $main_menu_html = ob_get_clean();
    echo apply_filters( 'udesign_get_top_main_menu', $main_menu_html );
}
add_action('udesign_top_wrapper_bottom', 'udesign_top_main_menu', 10);

What I need to override is just remove this two lines from udesign_nav_fallback() function:

$menu_html .= is_front_page() ? "<li class='current_page_item'>" : "<li>";
$menu_html .= '<a href="'.home_url().'"><span>'.esc_html__('Home', 'udesign').'</span></a></li>';

What I need to do in order to achieve that using the functions.php on the child theme?

Answer 1

You can't override the function(s). They aren't meant to be overwritten. See: "Override parent theme function that is not hooked or in the functions.php file" and "Is it possible to disable a function of a parent theme?". That is the direct answer to your question.

You can, however, almost certainly achieve the result you want by using the filter provided by the theme-- udesign_get_top_main_menu-- or any number of filters provided by wp_nav_menu() or by the Walker_Nav_menu class-- perhaps wp_nav_menu_objects or wp_nav_menu_items.

Per the question, you are wanting to remove:

$menu_html .= is_front_page() ? "<li class='current_page_item'>" : "<li>";
$menu_html .= '<a href="'.home_url().'"><span>'.esc_html__('Home', 'udesign').'</span></a></li>';

Ok. You probably need to use the filter provided in the code posted:

function udesign_strip($menu) {
  var_dump($menu);
  $menu_html = is_front_page() ? "<li class='current_page_item'>" : "<li>";
  $menu_html .= '<a href="'.home_url().'"><span>'.esc_html__('Home', 'udesign').'</span></a></li>';
  $menu = str_replace($menu_html,'',$menu);
  return $menu;
}
add_filter('udesign_get_top_main_menu','udesign_strip');

I don't like str_replaceing markup but that is probably the best way in this case.