无法在Symfony2 Twig扩展中重新声明类

Question

I'm creating a Twig extension and activating it with a service. Everything works great except I'm trying to simply use another class from my Twig extension.

The idea is to instantiate the new class then use it as needed. Instantiating is a problem as it errors with:

Error: Cannot redeclare class NewClass in .../Bundle/NewClass.php line 13

Surely it instantiates it once. Why is this happening?

namespace Bundle\Twig;

use Bundle\NewClass;

class NewExtension extends \Twig_Extension
{

    private $request;
    private $new_class;

    public function __construct($container) {

        //get the Request object   
        $this->request = $container->get('request');

        //instantiate new class
        $this->new_class = new NewClass();  // this part triggers the error

    }

    ///etc.

Answer 1

You should make your NewClass into a service and then inject that and the @request service into your twig extension rather than the container. Injecting the container directly is a bad idea apparently.

For example in your services..

services:
    # create new class as a instantiated service
    acme_demo.new_class:
        class: Acme\DemoBundle\NewClass
        arguments: [ '@request' ]

    acme_demo.twig.acme_extension:
        class: Acme\DemoBundle\Twig\AcmeExtension
        arguments: [ '@request', '@acme_demo.new_class' ]
            # inject the Request service and your class from above
        tags:
            - { name: twig.extension }

And then in your Twig extension

namespace Bundle\Twig;

use Bundle\NewClass;

class NewExtension extends \Twig_Extension
{
    private $new_class;

    public function __construct(NewClass $newClass) {
        $this->new_class = $newClass;
    }

    ///etc.

In your NewClass:

namespace Bundle;

class NewClass
{
    private $param1;
    private $param2;

    public function __construct(Request $request)
    {
        $this->param1 = $request->get('param1');
        $this->param2 = $request->get('param2');

        // You could also add some check in here to make sure they are valid.
    }