DIC container 101 in PHP

BasicDicContainer.php

<?php

class B {
    protected $c;
    public function __construct(C $c) {
        $this->c = $c;
    }
}

class C {}

class MyContainer
{
    protected $instances = array();

    public function __construct()
    {
        $this->instances = array(
            'B' => function (MyContainer $container) {
                return new B($container->get('C'));
            },

            'C' => function(MyContainer $container) {
                return new C();
            },
        );
    }

    public function get($name)
    {
        $cb = $this->instances[$name];

        if ($cb instanceof \Closure) {
            $this->instances[$name] = $cb($this);
        }

        return $this->instances[$name];
    }
}

$container = new MyContainer();
var_dump($container->get('B'));

https://gist.github.com/Ocramius/3151903#file-basicdiccontainer-php-L20

Actually - you're doing exactly the same thing.

@AmyStephen I am not sure what you mean by "exactly the same thing" - looking at https://gist.github.com/AmyStephen/5607606#comment-832169, the code is too stripped down to really follow all the steps.

There some sentences that I believe to be wrong:

Then, the Model requests the Database service in order to inject the database into the Model during construction.

and

That's why I passed the closure with the call back to the single entry point into the Container - so that - in this case - the model can getService('Database') to inject it in when it constructs the class.

Maybe it's just a language problem, but if I understand it correctly, you are trying to achieve lazy-loading by passing closures around your models.

The problem is essentially that the model itself (service? Don't call it "Model" please, "Model" could literally be anything :( ) requests services as far as I understand, and that breaks the DIP by making your object "aware" that it has to pull something.

It also breaks the LSP, since you now cannot inject a mock now, but instead rely on some callback-based signature, trusting the fact that the callback will retrieve a valid object.

In my opinion, you should first focus on writing it correct and forgetting about the lazy-loading problem. The DIC will eventually be able to produce lazy wrappers of your services.

I wrote extensively on this subject in an article that you've probably already read:

http://ocramius.github.io/blog/zf2-and-symfony-service-proxies-with-doctrine-proxies/ (read it later eventually)