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This tutorial is built using Drupal 8.0. The fundamental concepts of Drupal 8 - like services & routing - are still valid, but newer versions of Drupal *do* have major differences.

> Drupal 8 > Drupal 8: Under the Hood
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08.

Create a Service

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In RoarController, we use the $count variable to construct either a little roar or a big rooooooar, depending on what's in the URL:

15 lines | modules/dino_roar/src/Controller/RoarController.php
// ... lines 1 - 6
class RoarController
{
public function roar($count)
{
$roar = 'R'.str_repeat('O', $count).'AR!';
return new Response($roar);
}
}

Let's use our imagination. Pretend that this line is actually quite complicated. Maybe it takes 50 lines of code to figure this out! We could keep all 50 lines in this controller, but that sucks: it makes this function hard to read. Oh, and any code that lives in a controller can't be reused somewhere else. And don't even get me started on unit testing...

It's time to grow up and move out of our parent's basement. I mean, it's time to organize this code and put it somewhere else: in a new class that's independent of Drupal. In other words, in a service.

Creating the Service Class

In src/, create a new directory called Jurassic - this directory could be called anything - it's up to you to organize your services. Inside, create a new PHP class called RoarGenerator:

This class, well any class, needs to have a namespace that follows the standard of Drupal\ module name \ whatever directory or directories that you're in. This class is in one subdirectory called Jurassic. And make sure the class name matches the filename RoarGenerator:

12 lines | modules/dino_roar/src/Jurassic/RoarGenerator.php
// ... lines 1 - 2
namespace Drupal\dino_roar\Jurassic;
class RoarGenerator
{
// ... lines 7 - 10
}

This class has nothing to do with Drupal, it's completely our's. So you don't need to make it extend any weird Drupal core class. And we can make it do whatever we want. Create a public function getRoar() with a $length argument. Head over to RoarController and copy the code that creates that. Replace $count with $length and return that value:

12 lines | modules/dino_roar/src/Jurassic/RoarGenerator.php
// ... lines 1 - 4
class RoarGenerator
{
public function getRoar($length)
{
return 'R'.str_repeat('O', $length).'AR!';
}
}

Using a Service (the long way)

Great! Now our imaginary, complex code lives somewhere else. How do we use it? It's simple!

Create a $roarGenerator variable and set it new RoarGenerator();:

18 lines | modules/dino_roar/src/Controller/RoarController.php
// ... lines 1 - 4
use Drupal\dino_roar\Jurassic\RoarGenerator;
// ... lines 6 - 7
class RoarController
{
public function roar($count)
{
$roarGenerator = new RoarGenerator();
// ... lines 13 - 15
}
}

When I hit tab while typing the class, it auto-completes the line and adds the use statement above the class. Do not forget your use statements people! You'll get a "Class not found" error, and I'm pretty sure Dries gets a text message whenever it happens. So you know, try not to make him angry: he's really tall.

After instantiating the RoarGenerator object, update the last line to $roar = $roarGenerator->getRoar(); and pass it $count:

18 lines | modules/dino_roar/src/Controller/RoarController.php
// ... lines 1 - 9
public function roar($count)
{
$roarGenerator = new RoarGenerator();
$roar = $roarGenerator->getRoar($count);
return new Response($roar);
}
// ... lines 17 - 18

There is nothing special going on here: we moved the logic to an outside class, instantiated that object and then called a method on it. This has nothing to do with Drupal or Symfony or Dries getting text messages: it's just good object oriented code.

Let's give it a shot!

Go back to the browser and navigate to http://localhost:8000/the/dino/says/50. There's the scary roar meaning everything is working.

If you're thinking, "This seems like not a big deal - we're just moving code around". You're so right. Now keep watching!