Create Nav menu by Code in wordPress theme - php

Question

I am basically from .NET and Learning woocommerce themes ..I found this Code segment for Nav menu in Main page
<?php wp_nav_menu( array( 'theme_location' => 'primary' ) ); ?>
Edit :
I found Navigation Menu code in /httpdocs/ECOM/wp-includes / nav-menu.php
function wp_create_nav_menu( $menu_name ) {
return wp_update_nav_menu_object( 0, array( 'menu-name' => $menu_name ) );
}
and this one
function wp_update_nav_menu_object( $menu_id = 0, $menu_data = array() ) {
$menu_id = (int) $menu_id;
$_menu = wp_get_nav_menu_object( $menu_id );
$args = array(
'description' => ( isset( $menu_data['description'] ) ? $menu_data['description'] : '' ),
'name' => ( isset( $menu_data['menu-name'] ) ? $menu_data['menu-name'] : '' ),
'parent' => ( isset( $menu_data['parent'] ) ? (int) $menu_data['parent'] : 0 ),
'slug' => null,
);
// double-check that we're not going to have one menu take the name of another
$_possible_existing = get_term_by( 'name', $menu_data['menu-name'], 'nav_menu' );
if (
$_possible_existing &&
! is_wp_error( $_possible_existing ) &&
isset( $_possible_existing->term_id ) &&
$_possible_existing->term_id != $menu_id
) {
return new WP_Error( 'menu_exists',
/* translators: %s: menu name */
sprintf( __( 'The menu name %s conflicts with another menu name. Please try another.' ),
'<strong>' . esc_html( $menu_data['menu-name'] ) . '</strong>'
)
);
}
// menu doesn't already exist, so create a new menu
if ( ! $_menu || is_wp_error( $_menu ) ) {
$menu_exists = get_term_by( 'name', $menu_data['menu-name'], 'nav_menu' );
if ( $menu_exists ) {
return new WP_Error( 'menu_exists',
/* translators: %s: menu name */
sprintf( __( 'The menu name %s conflicts with another menu name. Please try another.' ),
'<strong>' . esc_html( $menu_data['menu-name'] ) . '</strong>'
)
);
}
$_menu = wp_insert_term( $menu_data['menu-name'], 'nav_menu', $args );
if ( is_wp_error( $_menu ) )
return $_menu;
do_action( 'wp_create_nav_menu', $_menu['term_id'], $menu_data );
return (int) $_menu['term_id'];
}
if ( ! $_menu || ! isset( $_menu->term_id ) )
return 0;
$menu_id = (int) $_menu->term_id;
$update_response = wp_update_term( $menu_id, 'nav_menu', $args );
if ( is_wp_error( $update_response ) )
return $update_response;
$menu_id = (int) $update_response['term_id'];
do_action( 'wp_update_nav_menu', $menu_id, $menu_data );
return $menu_id;
}
I searched some post and write some code to update menu
wp_update_nav_menu_object($menu_id, 0, array(
'menu-item-title' => __('Home'),
'menu-item-classes' => 'home',
'menu-item-url' => home_url( '/' ),
'menu-item-status' => 'publish'));
wp_update_nav_menu_object($menu_id, 0, array(
'menu-item-title' => __('Activity'),
'menu-item-classes' => 'activity',
'menu-item-url' => home_url( '/activity/' ),
'menu-item-status' => 'publish'));
wp_update_nav_menu_object($menu_id, 0, array(
'menu-item-title' => __('Members'),
'menu-item-classes' => 'members',
'menu-item-url' => home_url( '/members/' ),
'menu-item-status' => 'publish'));
But this is not working .. What am I missing here ?