The Separation of Concerns
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The Separation of Concerns
One down-side of our framework right now is that we need to copy and paste the
code in front.php each time we create a new website. 60 lines of code is
not that much, but it would be nice if we could wrap this code into a proper
class. It would bring us better reusability and easier testing to name just
a few benefits.
If you have a closer look at the code, front.php has one input, the
Request and one output, the Response. Our framework class will follow this
simple principle: the logic is about creating the Response associated with a
Request.
Let's create our very own namespace for our framework: Simplex. Move the
request handling logic into its own Simplex\\Framework class:
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// example.com/src/Simplex/Framework.php
namespace Simplex;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpKernel\Controller\ArgumentResolver;
use Symfony\Component\HttpKernel\Controller\ControllerResolver;
use Symfony\Component\Routing\Exception\ResourceNotFoundException;
use Symfony\Component\Routing\Matcher\UrlMatcher;
class Framework
{
protected $matcher;
protected $controllerResolver;
protected $argumentResolver;
public function __construct(UrlMatcher $matcher, ControllerResolver $controllerResolver, ArgumentResolver $argumentResolver)
{
$this->matcher = $matcher;
$this->controllerResolver = $controllerResolver;
$this->argumentResolver = $argumentResolver;
}
public function handle(Request $request)
{
$this->matcher->getContext()->fromRequest($request);
try {
$request->attributes->add($this->matcher->match($request->getPathInfo()));
$controller = $this->controllerResolver->getController($request);
$arguments = $this->argumentResolver->getArguments($request, $controller);
return call_user_func_array($controller, $arguments);
} catch (ResourceNotFoundException $e) {
return new Response('Not Found', 404);
} catch (\Exception $e) {
return new Response('An error occurred', 500);
}
}
}And update example.com/web/front.php accordingly:
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// example.com/web/front.php
// ...
$request = Request::createFromGlobals();
$routes = include __DIR__.'/../src/app.php';
$context = new Routing\RequestContext();
$matcher = new Routing\Matcher\UrlMatcher($routes, $context);
$controllerResolver = new ControllerResolver();
$argumentResolver = new ArgumentResolver();
$framework = new Simplex\Framework($matcher, $controllerResolver, $argumentResolver);
$response = $framework->handle($request);
$response->send();To wrap up the refactoring, let's move everything but routes definition from
example.com/src/app.php into yet another namespace: Calendar.
For the classes defined under the Simplex and Calendar namespaces to
be autoloaded, update the composer.json file:
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{
"...": "...",
"autoload": {
"psr-4": { "": "src/" }
}
}Note
For the Composer autoloader to be updated, run composer dump-autoload.
Move the controller to Calendar\Controller\LeapYearController:
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// example.com/src/Calendar/Controller/LeapYearController.php
namespace Calendar\Controller;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;
use Calendar\Model\LeapYear;
class LeapYearController
{
public function indexAction(Request $request, $year)
{
$leapyear = new LeapYear();
if ($leapyear->isLeapYear($year)) {
return new Response('Yep, this is a leap year!');
}
return new Response('Nope, this is not a leap year.');
}
}And move the is_leap_year() function to its own class too:
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// example.com/src/Calendar/Model/LeapYear.php
namespace Calendar\Model;
class LeapYear
{
public function isLeapYear($year = null)
{
if (null === $year) {
$year = date('Y');
}
return 0 == $year % 400 || (0 == $year % 4 && 0 != $year % 100);
}
}Don't forget to update the example.com/src/app.php file accordingly:
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$routes->add('leap_year', new Routing\Route('/is_leap_year/{year}', array(
'year' => null,
'_controller' => 'Calendar\Controller\LeapYearController::indexAction',
)));To sum up, here is the new file layout:
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example.com
├── composer.json
├── composer.lock
├── src
│ ├── app.php
│ └── Simplex
│ └── Framework.php
│ └── Calendar
│ └── Controller
│ │ └── LeapYearController.php
│ └── Model
│ └── LeapYear.php
├── vendor
│ └── autoload.php
└── web
└── front.phpThat's it! Our application has now four different layers and each of them has a well defined goal:
web/front.php: The front controller; the only exposed PHP code that makes the interface with the client (it gets the Request and sends the Response) and provides the boiler-plate code to initialize the framework and our application;src/Simplex: The reusable framework code that abstracts the handling of incoming Requests (by the way, it makes your controllers/templates easily testable -- more about that later on);src/Calendar: Our application specific code (the controllers and the model);src/app.php: The application configuration/framework customization.
