Trying to extend a Wordpress plugin, need to hook a function - wordpress

Question

I am trying to add some site-specific functionality to the Wordpress plugin Appointments+. When a user is making an appointment, they select certain services and enter information into some fields for confirmation.
What I want to do is add some code so the extra information fields are related to which service they choose. For example, if they choose Service A, they have to fill in some information and those fields are validated. But if they choose Service B, hide the fields and skip the validation.
Here is an example of the original code:
function post_confirmation() {
...some extra stuff
$values = explode( ":", $_POST["value"] );
$location = $values[0];
$service = $values[1];
do_action('app-additional_fields-validate');
...more stuff
}
Here is the kind of thing I want to do, but not alter this original plugin file:
function post_confirmation() {
...some extra stuff
$values = explode( ":", $_POST["value"] );
$location = $values[0];
$service = $values[1];
if (($service == 1) || ($service == 3)) {
do_action('app-additional_fields-validate');
}
...more stuff
}
I admit that I am new to using hooks and filters. I want to disable/enable that action based on a variable in the function. How can I do that with another hook/filter?
Thank you.

Answer 1

Unhook the hook used for calling post_confirmation and override this function from your functions.php like
remove_action( 'current_action_hook', 'post_confirmation' );
add_action( 'current_Action_hook', 'post_custom_confirmation' );
function post_custom_confirmation(){
...some extra stuff
$values = explode( ":", $_POST["value"] );
$location = $values[0];
$service = $values[1];
if (($service == 1) || ($service == 3)) {
do_action('app-additional_fields-validate');
}
...more stuff
}
I think this should work, I have used this way during a woocommerce plugin development before nearly 2 months below is working code example , so that if you need any modification on code above, you can take reference .
remove_action( 'woocommerce_checkout_order_review', 'woocommerce_order_review', 10 );
add_action( 'woocommerce_checkout_order_review', 'pk_order_review', 10, 1 );
function pk_order_review($template) {
global $woocommerce;
$template = wc_get_template ( 'checkout/review-order.php', FALSE, FALSE, untrailingslashit( plugin_dir_path( __FILE__ ) ) . '/templates/');
return $template;
exit;
}
Another way you can do it is
add_action( 'app-additional_fields-validate', 'foo' );
function foo(){
if (($service == 1) || ($service == 3)) {
/* Your stuffs */
}
}

Answer 2

This is actually part answer, part new question. If that is possible to do here.
So, I finally found a way to affect the desired function.
The function I was trying to modify is contained in a class so, I did something like this:
class my_Check extends Appointments {
function __construct() {
$this->unregister_parent_hook();
add_action( 'wp_ajax_post_confirmation', array( $this, 'post_confirmation' ) );
add_action( 'wp_ajax_nopriv_post_confirmation', array( $this, 'post_confirmation' ) );
}
function unregister_parent_hook() {
global $appointments; //this was the object created with the parent class
remove_action( 'wp_ajax_post_confirmation', array( $appointments, 'post_confirmation' ) );
remove_action( 'wp_ajax_nopriv_post_confirmation', array( $appointments, 'post_confirmation' ) );
}
function post_confirmation() {
...do the stuff with my mods...
}
}
$new_Check = new my_Check();
Only, I have a new problem now. The parent class does a lot more in the __construct() (many 'add_action()'s, etc.). And $this is populated with a lot more data. The problem is, these other things and data do not seem to be carrying over into the child class. I tried adding a parent::__construct() in the child's __construct() function, but that did not seem to work.
The code with my mods works except for things that need more data in the $this carried over from the parent class.
How can I maintain all the parent class's variable, functions, hooks & filters, etc. into the child class?