Using a filter to modify Genesis wp_nav_menu

Question

Genesis framework applies filters to the wp_nav_menu(). What I want to do is 2 things.

1 change the menu class via a filter

2 add a menu id via a filter

Here is the function I am trying to add a filter to.

add_action( 'genesis_after_header', 'genesis_do_nav' );
/**
 * Echoes the "Primary Navigation" menu.
 *
 * The preferred option for creating menus is the Custom Menus feature in
 * WordPress. There is also a fallback to using the Genesis wrapper functions
 * for creating a menu of Pages, or a menu of Categories (maintained only for
 * backwards compatibility).
 *
 * Either output can be filtered via 'genesis_do_nav'.
 *
 * @since 1.0.0
 *
 * @uses genesis_get_option() Get theme setting value
 * @uses genesis_nav() Use old-style Genesis Pages or Categories menu
 * @uses genesis_structural_wrap() Adds optional internal wrap divs
 */
function genesis_do_nav() {

    /** Do nothing if menu not supported */
    if ( ! genesis_nav_menu_supported( 'primary' ) )
        return;

    if ( genesis_get_option( 'nav' ) ) {
        if ( has_nav_menu( 'primary' ) ) {
            $args = array(
                'theme_location' => 'primary',
                'container'      => '',
                'menu_class'     => genesis_get_option( 'nav_superfish' ) ? 'menu menu-primary superfish' : 'menu menu-primary',
                'echo'           => 0,
            );

            $nav = wp_nav_menu( $args );
        } elseif ( 'nav-menu' != genesis_get_option( 'nav_type', 'genesis-vestige' ) ) {
            $args = array(
                'theme_location' => 'primary',
                'menu_class'     => genesis_get_option( 'nav_superfish' ) ? 'menu menu-primary superfish' : 'menu menu-primary',
                'show_home'      => genesis_get_option( 'nav_home', 'genesis-vestige' ),
                'type'           => genesis_get_option( 'nav_type', 'genesis-vestige' ),
                'sort_column'    => genesis_get_option( 'nav_pages_sort', 'genesis-vestige' ),
                'orderby'        => genesis_get_option( 'nav_categories_sort', 'genesis-vestige' ),
                'depth'          => genesis_get_option( 'nav_depth', 'genesis-vestige' ),
                'exclude'        => genesis_get_option( 'nav_exclude', 'genesis-vestige' ),
                'include'        => genesis_get_option( 'nav_include', 'genesis-vestige' ),
                'echo'           => false,
            );

            $nav = genesis_nav( $args );
        }

        $nav_output = sprintf( '%2$s%1$s%3$s', $nav, genesis_structural_wrap( 'nav', 'open', 0 ), genesis_structural_wrap( 'nav', 'close', 0 ) );

        echo apply_filters( 'genesis_do_nav', $nav_output, $nav, $args );
    }

}

I was initially trying to add_filter where I can modify the $args to change the class and add an id.

How do I go about doing this?

Here is my 'best guess'

function xyz_modify_nav($args) {
    $args = array(
       'menu_class' => 'xyz',
       'menu_id'    => 'custom'
    );
}
add_filter('genesis_do_nav', 'xyz_modify_nav',20);

Answer 1

This new updated version of Evan's Code works with Genesis 1.9 and fixes the bug of displaying all navigation items.

/*
 * Add classes to Genesis Navigation
 * Tested with Genesis 1.9 (Beta)
 * 29.12.2012
 */
add_filter( 'genesis_do_nav', 'override_do_nav', 10, 3 );
function override_do_nav($nav_output, $nav, $args) {

    $args['menu_id'] = 'the_id_you_want';
    $args['menu_class'] = 'class1 class2'; // replace what was there 
    $args['menu_class'] .= ' nav-bar'; // or append to it

    if ( genesis_get_option( 'nav' ) ) {
        if ( has_nav_menu( 'primary' ) ) {          
            $nav = wp_nav_menu( $args );            
        } elseif ( 'nav-menu' != genesis_get_option( 'nav_type', 'genesis-vestige' ) ) {
            $nav = genesis_nav( $args );
        }
    }

    return sprintf( '<div id="nav">%2$s%1$s%3$s</div>', $nav, genesis_structural_wrap( 'nav', 'open', 0 ), genesis_structural_wrap( 'nav', 'close', 0 ) ); 
}

Cheers Daniel

Answer 2

The function that Genesis gives you to use does not give you the option of altering those args before the wp_nav_menu function is called with them. The filter merely passes those to your filter callback function to use.

Updated Solution

My original answer was much too long-winded. This is much simpler and should do exactly what you want.

add_filter( 'genesis_do_nav', 'override_do_nav', 10, 3 );
function override_do_nav($nav_output, $nav, $args) {

    $args['menu_id'] = 'the_id_you_want';
    $args['menu_class'] = 'class1 class2'; // replace what was there
    $args['menu_class'] .= ' class3'; // or append to it

    // check which function should be used to build the nav
    // rebuild the nav using the updated arguments
    if(array_key_exists('type', $args))
        $nav = wp_nav_menu( $args );
    else
        $nav = genesis_nav( $args );

    // return the modified result
    return sprintf( '%2$s%1$s%3$s', $nav, genesis_structural_wrap( 'nav', 'open', 0 ), genesis_structural_wrap( 'nav', 'close', 0 ) );

}