Symfony2中的服务

Question

I'm trying to get some service (eg session) from outside of controller.

Please, explain how to do this right-way.

Answer 1

There are many different ways, all having pros and cons.

First, every service is some kind of object, so you can always just create the object in question yourself. You may be forced to deal with many references, but it's possible. This undermines the idea of Dependency Injection, so it's not what you should do!

The second way is inject the service into your class:

class MyClass{

    public function __construct($session){
        // ...
    }
}

class MyContainer extends Controller{

    public function SomeKindOfAction(){
        $myClass = new MyClass($this->get('session'));
    }
}

This might be ok if you only use the class within your Controller. If you have more nested relations, like in MyClass, you create another class where you need the session, you might run into tight coupling (which is to avoid) as well as complexity issues.

The best way is to create your own service and injecting the things you need there. There are many documentations out there, so I'll just give a short example using MyClass above.

services.yml:

services:
    my.myClass:
        class: /Acme/DefaultBundle/MyStuff/MyClass
        arguments: ["@session"]

Now your Class is as service (who would guess it's that easy!) and you can use it within your controller:

class MyContainer extends Controller{

    public function SomeKindOfAction(){
        $myClass = $this->get('my.myClass');
    }
}

Now you don't have to think about constructor and how to get your objects, the DI-Container will do it for you. If you want to know more, read here .