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app/data/pages/08-inversion-of-control.md

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+[<< previous](07-dispatching-to-a-class.md) | [next >>](09-dependency-injector.md)
+
+### 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](http://en.wikipedia.org/wiki/Inversion_of_control). This means that
+instead of giving the class the responsiblity of creating the object it needs, you just ask for them. This is done
+with [dependency injection](http://en.wikipedia.org/wiki/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
+<?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:
+
+```php
+$handler = new $className($response);
+```
+
+Of course we need to also update all the other handlers.
+
+[<< previous](07-dispatching-to-a-class.md) | [next >>](09-dependency-injector.md)