<?php

class A extends Nette\Object {

	// callbacks
	public $beforeRender;

	public $template;

	public function __construct() {
		$this->template = (object) NULL;
	}

	public function render() {
		$this->beforeRender($this);
		print_r($this->template);
	}
}

$a = new A;

$a->beforeRender[] = function($self) {
	$self->template->a = 'a';
};

$a->beforeRender[] = function($self) {
	$self->template->b = 'b';
};

$a->render();