no-framework-tutorial/08-inversion-of-control.md

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Inversion of Control

In the last part you have set up a controller class and generated our Http-Response-object in that class, but if we want to switch to a more powerfull Http-Implementation later, or need to create our own for some special purposes, then we would need to edit every one of our request handlers to call a different constructor of the class.

The sane option is to use inversion of control. This means that instead of giving the class the responsibility of creating the object it needs, you just ask for them. This is done with dependency injection.

If this sounds a little complicated right now, don't worry. Just follow the tutorial and once you see how it is implemented, it will make sense.

Change your Hello action to the following:

<?php declare(strict_types = 1);

namespace Lubian\NoFramework\Action;

use Psr\Http\Server\RequestHandlerInterface;
use Psr\Http\Message\ServerRequestInterface as Request;
use Psr\Http\Message\ResponseInterface as Response;

final class Hello implements \Psr\Http\Server\RequestHandlerInterface;
{
    public function __construct(
        private Response $response
    ) {}
    public function handle(Request $request): Response
    {
        $name = $request->getAttribute('name', 'Stranger');
        $body = $this->response->getBody();
        
        $body->write('Hello ' . $name . '!');
        
        return $this->response
            ->withBody($body)
            ->withStatus(200);
    }
}

Now the code will result in an error because we are not actually injecting anything. So let's fix that in the Bootstrap.php where we dispatch when a route was found:

$handler = new $className($response);

Of course we need to also update all the other handlers.

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