Bootstrap drop down menu with wp_nav_menu

Question

I am trying to build a Wordpress theme with boostrap, but the nav menu is giving me some trouble. I would like the dropdown to work like boostraps dropdown, but I do not know how to do this.

This is my menu:

<ul class="nav">
   <?php wp_nav_menu( array( 'items_wrap' => '%3$s' ) ); ?>
</ul>

This is what I have in my functions.php for the menu:

add_action('after_setup_theme', 'blankslate_setup');
function blankslate_setup(){
register_nav_menus(
array( 'main-menu' => __( 'Main Menu', 'blankslate' ) )
);
}

function my_wp_nav_menu_args( $args = '' )
{
    $args['container'] = false;
    return $args;
} // function

add_filter( 'wp_nav_menu_args', 'my_wp_nav_menu_args' );

When I add a submenu item (via Appearance - Menus) this is what is currently generated:

<ul class="nav">
    <li id="menu-item-18" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-18"><a href="#">Parent</a>
        <ul class="sub-menu">
                <li id="menu-item-19" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-19"><a href="#">Child</a></li>
        </ul>
    </li>
</ul>

For my menu to work with bootstrap I need the menu to be generated like:

<ul class="nav">
    <li class="dropdown"><a href="#" class="dropdown-toggle" data-toggle="dropdown">Parent <b class="caret"></b></a>
        <ul class="dropdown-menu">
            <li><a href="#">Child</a></li>
        </ul>
    </li>
</ul>

So I need:

• To add the class "dropdown", if a menu-item has child-items.
• To add class="dropdown-toggle" data-toggle="dropdown" to the .dropdown a element
• To add <b class="caret"></b> after the Dropdown-menu name (inside the .dropdown a element)
• To add class="dropdown-menu" to <ul class="sub-menu">

Hope someone can help!

Answer 1

You will need to write a custom walker extending Walker_Nav_Menu, more or less like so:

class My_Custom_Nav_Walker extends Walker_Nav_Menu {

   function start_lvl(&$output, $depth = 0, $args = array()) {
      $output .= "\n<ul class=\"dropdown-menu\">\n";
   }

   function start_el(&$output, $item, $depth = 0, $args = array(), $id = 0) {
       $item_html = '';
       parent::start_el($item_html, $item, $depth, $args);

       if ( $item->is_dropdown && $depth === 0 ) {
           $item_html = str_replace( '<a', '<a class="dropdown-toggle" data-toggle="dropdown"', $item_html );
           $item_html = str_replace( '</a>', ' <b class="caret"></b></a>', $item_html );
       }

       $output .= $item_html;
    }

    function display_element($element, &$children_elements, $max_depth, $depth = 0, $args, &$output) {
        if ( $element->current )
        $element->classes[] = 'active';

        $element->is_dropdown = !empty( $children_elements[$element->ID] );

        if ( $element->is_dropdown ) {
            if ( $depth === 0 ) {
                $element->classes[] = 'dropdown';
            } elseif ( $depth === 1 ) {
                // Extra level of dropdown menu, 
                // as seen in http://twitter.github.com/bootstrap/components.html#dropdowns
                $element->classes[] = 'dropdown-submenu';
            }
        }

    parent::display_element($element, $children_elements, $max_depth, $depth, $args, $output);
    }
}

Not sure of what you need with points 3 and 4, though.

Answer 2

To fix the dropdown menu problem you should:

go to class-wp-bootstrap-navwalker.php file

look for

$atts['data-toggle'] ="dropdown";

and replace it with

$atts['data-bs-toggle'] ="dropdown";