Symfony2无法在依赖注入中实例化接口

Question

I have a problem when I try to create a service in Symfony2.

This is my services.yml

services:
    Menu:
        class:  My\WebBundle\Classes\System\Menu        
        arguments: [@service_container]

This is my service Menu:

namespace My\WebBundle\Classes\System;

use Symfony\Component\DependencyInjection\ContainerInterface as Container;

Class Menu{
    private $container;

    public function __construct(Container $container) {                
        $this->container = $container;                
    }

    public function getMenu($section) {
        return "hello";
    }
}

When in a controller I do:

$menu = $this->get('Menu');

I get:

FatalErrorException: Error: Cannot instantiate interface My\\WebBundle\\Classes\\System\\Menu in ...\\cache\\dev\\appDevDebugProjectContainer.php line 1522

Of course I cleaned cache.

Answer 1

Change your use statement to;

use Symfony\Component\DependencyInjection\Container;

Also I would redeclare the arguments enclosing the service name in quotes.

services:
    Menu:
        class:  My\WebBundle\Classes\System\Menu        
        arguments: ["@service_container"]

I would question why you are injecting the whole container though.
Why not just inject the parts you need?

If you are defining your controller as a service also, you can access your Menu service by injecting that into your controller.

EXTRA AS PER COMMENT REQUEST ;

services:
        Menu:
            class:  My\WebBundle\Classes\System\Menu        
            arguments: ["@router"]

And class would look like;

<?php 
namespace My\WebBundle\Classes\System;

use Symfony\Component\Routing\RouterInterface;

Class Menu{
    private $router;

    public function __construct(RouterInterface $router) {                
        $this->router = $router;                
    }

    public function getMenu($section) {
        return "hello";
    }
}