Symfony 2.8: Can't manage to use container in custom class - php

Question

I would like to use $this->container->get in a custom class I've created.
I've done my reading and found out that I should use ContainerInterface in the constructor, which I do, but I still get this error:
Error: Call to a member function get() on a non-object
Here is the code:
MyClass.php
namespace path\to\MyClass;
use Symfony\Component\DependencyInjection\ContainerInterface;
class MyClass {
private $container;
public $user_id;
public function __contruct(ContainerInterface $container) {
$this->container = $container;
$this->user_id = $user_id;
return $this;
}
/**
* #param string $data Some data
* #return array A response
*/
public function generatePDF($data)
{
// Create the folders if needed
$pdf_folder = __DIR__.'/../../../../web/pdf/'.$this->user_id.'/';
if(!file_exists($pdf_folder))
mkdir($pdf_folder, 0755, TRUE);
$file_id = "abc1";
// Set the file name
$file = $pdf_folder.$file_id.'.pdf';
// Remove the file if it exists to prevent errors
if(file_exists($file)) {
unlink($file);
}
// Generate the PDF
$this->container->get('knp_snappy.pdf')->generateFromHtml(
$this->renderView(
'StrimeGlobalBundle:PDF:invoice.html.twig',
$data
),
$file
);
}
}
Do you guys have any idea of what could be the problem?
Thanks for your help.

Answer 1

You need to declare your class as a service in the Symfony configuration.
Please have a look to the Symfony service container page.
Here is an explanation to inject the container in the constructor:
# services.yml
services:
app.my_class:
class: TheBundle\Service\MyClass
arguments: ['#service_container']
Or as said JimL in comment, you can inject the service you need (which is recommanded):
class MyClass
{
private $pdfService;
public function __construct(\Your\Service\Namespace\Class $pdfService)
{
$this->pdfService = $pdfService;
}
// ...
}
And in your service.yml file
# services.yml
services:
app.my_class:
class: TheBundle\Service\MyClass
arguments: ['#knp_snappy.pdf']
The container can also be injected with a setter. See this link
Hope this helps!

Answer 2

Your class cannot "see" any service (including the container) unless you "inject" it. In YourCustomBundle/Resources/config/services.xml you need to define the service and it's dependencies. Read up on Dependency Injection and it should make more sense.
Also, #JimL is right, you shouldn't inject the entire container to access one service, simply inject the one service (knp_snappy.pdf)