Using Woocommerce Hooks in a Wordpress Plugin - wordpress

Question

I created a sample plugin for using woocommerce hooks. Basically my requirement was to add some javascript to the footer of the wordpress page based on some woocommerce hooks. However, those hooks don't seem to get fired at all. I have woocommerce installed. If I put the same code in theme's function file, the javsacript gets added, but not from the plugin.
In the plugin, there are three actions. The first action is a plain wp_footer action which works and js is added. the remaining two are woocommerce actions and are not getting fired. Can anyone please help? I am sure I am calling the hooks the wrong way but I can't figure out.
<?php
/*
* Plugin Name: Demo Woo Plugin
* Plugin URI:
* Description:
* Version: 1.0
* Author:
* Author URI:
* License: GPLv2
*/
/*
*/
if(!class_exists('Demowoo')) {
class Demowoo {
var $plugin_url;
var $plugin_dir;
public function __construct() {
global $woocommerce;
$this->plugin_url = trailingslashit( WP_PLUGIN_URL . '/' . dirname(plugin_basename(__FILE__)) );
$this->plugin_dir = trailingslashit( plugin_dir_path(__FILE__) );
add_action( 'wp_footer', array($this, 'demowoo_content') );
// initiate woocommerce hooks and activities
add_action('woocommerce_init', array($this, 'on_woocommerce_init'));
add_action('woocommerce_after_cart_contents', 'cart_page_visited');
}
public function install() {
}
public function deactivate() {
}
/**
* Append the required javascript.
*/
public function demowoo_content() {
echo '<script type="text/javascript">console.log("Demo Plugin Content");</script>';
}
public function on_woocommerce_init() {
add_action('wp_footer', 'woocommerce_initialized');
}
public function woocommerce_initialized() {
echo '<script type="text/javascript">console.log("JS through woo commerce init.");</script>';
}
public function cart_page_visited() {
add_action('wp_footer', 'demo_woo_add_to_cart');
}
public function demo_woo_add_to_cart() {
echo '<script type="text/javascript">console.log("JS for added_to_cart on the cart page");</script>';
}
} // End class
$Demowoo = new Demowoo();
if($Demowoo) {
register_activation_hook( __FILE__, array(&$Demowoo, 'install'));
}
}

Answer 1

All your calls of add_action should use the form array($this, 'method_name') in their second parameter, like the first hook on wp_footer. This is because you are hooking methods of an object, not functions.
If you just write the name of the method WP will look for a global function with that name, not a class method. Since there are no global functions with those names, nothing happens.
The array syntax allows WP to know not only the method name but which object it should be invoked from. PHP cannot just invoke an object method without having an instance of the object, so you need to provide one to the hooking system. With the style to define plugins that you're using here the object instance is usually always $this.