Read from parameters in Symfony 3.4 getParameter null - symfony

Question

I can't read a parameter from parameters.yml in my controller.
I want to do this:
//My Controller
class ExampleController extends Controller
{
function someMethod($argument)
{
dump($this->getParameter('free_proxy'));die();
and in parameters.yml I got:
parameters:
free_proxy: "http://xxx:8080"
I get an error: Call to a member function getParameter() on null
I've tested some solutions like adding some services and using get and stuff but nothing works.
EDIT: also, I tried this:
services:
_defaults:
autowire: true
autoconfigure: true
public: false
bind:
$freeProxy: '%free_proxy%'
Then using:
$this->container->getParameter('free_proxy');
But I got an error: Unused binding "$freeProxy" in service...

Answer 1

So there are two mysteries here. First is why is the container not being injected which in turn causes getParameter to fail. And second, why does bind generate that unused binding error.
You did not show your routing but I suspect that somewhere along the line you actually have:
$exampleController = new ExampleController();
If so then this explains why getParameter is failing. You really need to let Symfony create the controller based on the route. Otherwise the container is not injected and other controller magic is skipped.
I installed a fresh 3.4 app with the old directory structure and added a parameter
composer create-project symfony/framework-standard-edition s34
# app/config/parameters.yml
parameters:
free_proxy: "http://xxx:8080"
I then tweaked the default controller using the default route annotation:
class DefaultController extends Controller
{
/**
* #Route("/", name="homepage")
*/
public function indexAction(Request $request)
{
$freeProxy = $this->getParameter('free_proxy');
// replace this example code with whatever you need
return $this->render('default/index.html.twig', [
'base_dir' => realpath($this->getParameter('kernel.project_dir')).DIRECTORY_SEPARATOR.$freeProxy,
]);
}
}
And everything worked as expected. The Symfony request handler takes care of injecting the container and thus gives you access to the parameters. If you cannot get this working then please update your question with your routing information.
I then took a look at the bind issue. You really want to inject these parameters instead of pulling them. I updated services.yml
# app/config/services.yml
services:
bind:
$freeProxy: '%free_proxy%'
And started getting those unused binding errors. It turns out that bind does not work for action injection. Not really sure why. I don't use it much but I really would have expected that just adding $freeProxy to your action method would work. In any event, here is a working example of the proper way to do things.
class ExampleController extends Controller
{
private $freeProxy;
public function __construct($freeProxy)
{
$this->freeProxy = $freeProxy;
}
/**
* #Route("/example", name="example")
*/
function someMethod()
{
dump($this->freeProxy);
dump($this->getParameter('free_proxy'));die();
}
}
I then went to a fresh 4.2 project and tried action injection:
class IndexController extends AbstractController
{
public function index($freeProxy)
{
return new Response("Index $freeProxy");
}
}
Action injection works as expected for 4.2 but not 3.4. Constructor injection works fine in either version.

Answer 2

documentation show like this :
parameters.yml :
parameters:
mailer.transport: sendmail
to set :
$container->setParameter('mailer.transport', 'sendmail');
to get :
$container->getParameter('mailer.transport');