ajax call to controller function without action

Question

I need to add a block to a page. In a block adding dialog I have a select box which I need to fill with data received from ajax prior to saving the block (it cannot be saved unless I select the option).

The problem is the ajax call is usually to a controller action which doesn't exist until I save the block which I can't save before the option is selected. How can I make an ajax call to any other non-action function prior to the block saving? Can it be any other controller function or it must only be an action_function? Is this possible?

[UPDATE]

I'm trying with routes. Declared a route in the package controller:

$this->app->make(Router::class)->register('/api/get_forum_posts', '\Concrete\Package\AbForum\Src\Forum\MyFunctions::get_forum_posts', null, [], [], '', [], ['GET']);

but it says:

Exception Occurred: /srv/www/htdocs/c584/concrete/src/Controller/ApplicationAwareControllerResolver.php:89 Class "\Concrete\Package\AbForum\Src\Forum\MyFunctions" does not exist.

but the class MyFunctions IS in that folder packages/ab_forum/src/Forum/MyFunctions.php

Answer 1

I got it. The following works.

In the package controller:

protected $pkgAutoloaderRegistries = [
    'src/Forum' => 'Forum'
];

public function on_start()
{
    $this->app->make(Router::class)->register('/api/get_forum_posts', 'Forum\MyFunctions::getForumPostsJson', null, [], [], '', [], ['GET']);
...
}

The MyFunctions controller class in packages/ab_forum/src/Forum/MyFunctions.php:

namespace Forum;

use Concrete\Core\Controller\AbstractController;

class MyFunctions extends AbstractController
{
    public function getForumPostsJson()
    {
        $data = $request->request->all();
        ...
        echo json_encode($json);
        exit;
    }
}

The block form with ajax:

$.ajax({
    url: '<?php echo Url::to('api/get_forum_posts'); ?>',
    type: 'GET',
    data: {
        topic: topic.val(),
        date: date.val(),
    },
})
.done(function(data) {
    ...
});