How to call a class method as a callback function in wordpress custom endpoint?

I have a custom endpoint which looks like this:

add_action( 'rest_api_init', function () {
register_rest_route( 't2mchat/v2', '/get_curr_user_lang', array(
'methods' => 'GET',
'callback' => 'get_user_lang'
));
});


I was able to call the callback function "get_user_lang" when it wasn't a class based method. But once I converted it to a class based method, I wasn't able to call it.

My class looks like this:

<?php
namespace T2mchat\TokenHandler;


class TokenHandler {
function get_user_lang() {
return "client_langs";
}
}
?>

and my new endpoint looks like this:

$t2m = new T2mchat\TokenHandler\TokenHandler();
add_action( 'rest_api_init', function () {
register_rest_route( 't2mchat/v2', '/get_curr_user_lang', array(
'methods' => 'GET',
'callback' => array($t2m, 'get_user_lang')
));
});

Anyone have any idea on how to call a class based method in WordPress Rest API custom endpoints?

Class methods in WordPress Hooks should be set via 2 dimensional array.

add_action( 'rest_api_init', function () {
register_rest_route( 't2mchat/v2', '/get_curr_user_lang', array(
'methods' => 'GET',
'callback' => array($class_object,'get_user_lang')
));
});

If you're using a static method of the same class, the array() solution doesn't work. I had to use the "magic" constant `__CLASS__` :

'callback' => __CLASS__ . '::get_posts',

And to add an action using this custom class with another static method as callback I had to use this notation:

require_once( get_template_directory() . "/inc/classes/Rest/Posts.php" );
add_action( 'rest_api_init', 'Custom\Namespace\Posts::register_routes');

If the hook is called within the class if-self and yout callback method is defined there:

add_action( 'rest_api_init', function () {
register_rest_route( 't2mchat/v2', '/get_curr_user_lang', array(
'methods' => 'GET',
'callback' => array($this,'get_user_lang')
));
});

If from different class:

add_action( 'rest_api_init', function () {
register_rest_route( 't2mchat/v2', '/get_curr_user_lang', array(
'methods' => 'GET',
'callback' => array(new className,'get_user_lang')
));
});

If this solution is not working, a bit more details of your problem will help in defining.