1.
How I started to love what
they call
Design Patterns
@samuelroze

2.
Samuel Rozé
VP of Engineering @ Birdie
Symfony
ContinuousPipe
Tolerance

3.
I started years ago...

4.
I probably wrote that
<?php
include 'header.php';
include 'pages/'. $_GET['page'].'.php';
include 'footer.php';

5.
At some point I used Symfony
class EntityController extends AbstractController
{
public function action(
EntityManagerInterface $entityManager,
string $identifier
) {
$entity = $entityManager->getRepository(Entity::class)
->find($identifier);
return $this->render('my-template.html.twig', [
'entity' => $entity,
]);
}
}

6.
Then I updated my entity...
public function action(
EntityManagerInterface $entityManager,
Request $request,
string $identifier
) {
// ...
if ($request->isMethod('POST')) {
$form->handleRequest($request);
if ($form->isValid()) {
$entity = $form->getData();
$entityManager->persist($entity);
$entityManager->flush();
}
}
// ...
}

7.
Then I sent an email
// ...
if ($form->isValid()) {
$entity = $form->getData();
$entityManager->persist($entity);
$entityManager->flush();
$mailer->send(
(new Email())
->setTo('samuel.roze@gmail.com')
->setBody('Very long text here...')
->setFrom('My super application')
// ...
);
}
// ...

8.
Well... that's long!
class EntityController extends AbstractController
{
public function action(
EntityManagerInterface $entityManager,
MailerInterface $mailer,
Request $request,
string $identifier
) {
$entity = $entityManager->getRepository(Entity::class)
->find($identifier);
$form = $this->createForm(EntityFormType::class, $entity);
if ($request->isMethod('POST')) {
$form->handleRequest($request);
if ($form->isValid()) {
$entity = $form->getData();
$entityManager->persist($entity);
$entityManager->flush();
$mailer->send(
(new Email())
->setTo('samuel.roze@gmail.com')
->setBody('Very long text here...')
->setFrom('My super application')
);
}
}
return $this->render('my-template.html.twig', [
'entity' => $entity,
]);
}
}

9.
And then...
It became un-maintanable

10.
Design Patterns

11.
A general reusable solution
to a commonly occurring
problem within a given
context.
1
Wikipedia

12.
All the design patterns do
the same thing: control the
information flow.
1
Anthony Ferrara

13.
Let's do some refactoring!

14.
Why do we refactor?
4 We want to reuse code
4 So we delegate the responsibilities
4 And improve the readability
4 And therefore we ensure maintainability
4 By doing so we enable change

15.
Adapter

16.
Adapter
interface EntityRepository
{
public function find(string $identifier): ?Entity;
public function save(Entity $entity): Entity;
}

17.
Adapter
final class DoctrineEntityRepository implements EntityRepository
{
private $entityManager;
public function __construct(EntityManagerInterface $entityManager)
{
$this->entityManager = $entityManager;
}
public function find(string $identifier) : ?Entity
{
return $this->entityManager->getRepository(Entity::class)
->find($identifier);
}
// ...
}

18.
Adapter
final class DoctrineEntityRepository implements EntityRepository
{
// ...
public function save(Entity $entity) : Entity
{
$entity = $this->entityManager->merge($entity);
$this->entityManager->persist($entity);
$this->entityManager->flush();
return $entity;
}
}

19.
class EntityController extends AbstractController
{
public function action(
EntityRepository $entityRepository,
Request $request,
string $identifier
) {
$entity = $entityRepository->find($identifier);
// ...
if ($form->isValid()) {
$entityRepository->save($entity);
$mailer->send(
(new Email())->setBody('Hey, something was updated!')
);
}
}
}

20.
class EntityController
{
public function __construct(EntityRepository $entityRepository, /** ... **/)
{ /** ... **/ }
public function action(Request $request, string $identifier)
{
$entity = $this->entityRepository->find($identifier);
// ...
if ($form->isValid()) {
$this->entityRepository->save($entity);
$this->mailer->send(
Swift_Message::newInstance()
->setBody('Hey, something was updated!')
);
}
}
}

21.
Store the entity in-memory?
final class InMemoryEntityRepository implements EntityRepository
{
private $entities = [];
public function find(string $identifier) : ?Entity
{
return $this->entities[$identifier] ?? null;
}
public function save(Entity $entity) : Entity
{
$this->entities[$entity->getIdentifier()] = $entity;
return $entity;
}
}

22.
Multiple implementations: The Yaml
bits
# config/services.yaml
services:
_defaults:
autoconfigure: true
autowire: true
# ...
AppEntityRepository:
alias: AppInfrastructureDoctrineDoctrineEntityRepository

23.
Fast tests?
# config/services_test.yaml
services:
# ...
AppEntityRepository:
alias: AppTestsInMemoryInMemoryEntityRepository

24.
Event Dispatcher

25.
Dispatching the event
class MyController
{
public function __construct(
EntityRepository $entityRepository,
EventDispatcherInterface $eventDispatcher
) { /* ... */ }
public function action(Request $request, string $identifier)
{
// ...
if ($form->isValid()) {
$this->entityRepository->save($entity);
$this->eventDispatcher->dispatch(
EntitySaved::NAME,
new EntitySaved($entity)
);
}
// ...
}
}

26.
An event
class EntitySaved extends Event
{
const NAME = 'entity.saved';
private $entity;
public function __construct(Entity $entity)
{
$this->entity = $entity;
}
public function getEntity() : Entity
{
return $this->entity;
}
}

27.
A listener
final class SendAnEmailWhenEntityIsSaved
{
public function __construct(MailerInterface $mailer)
{ /** ... **/ }
public function onEntitySaved(EntitySaved $event)
{
$this->mailer->send(/** something **/);
}
}

28.
Wiring it
final class SendAnEmailWhenEntityIsSaved implements EventSubscriberInterface
{
// ...
public static function getSubscribedEvents()
{
return [
EntitySaved::NAME => 'onEntitySaved',
];
}
public function onEntitySaved(EntitySaved $event)
{
// ...
}
}

29.
What is the point?
4 The controller just have to dispatch this event
4 We can create another listener easily
4 Much easier to group things per feature

30.
Decorator

31.
final class DispatchAnEventWhenEntityIsSaved implements EntityRepository
{
public function __construct(
EntityRepository $decoratedRepository,
EventDispatcherInterface $eventDispatcher
) { /** ... **/ }
public function find(string $identifier) : ?Entity
{
return $this->decoratedRepository->find($identifier);
}
public function save(Entity $entity) : Entity
{
$saved = $this->decoratedRepository->save($entity);
$this->eventDispatcher->dispatch(
EntitySaved::NAME, new EntitySaved($saved)
);
return $saved;
}
}

32.
Decorates the repository: Plumbing!
# config/services.yaml
services:
# ...
AppEntityRepositoryDispatchAnEventWhenEntityIsSaved:
decorates: AppEntityRepository
arguments:
- "@AppEntityRepositoryDispatchAnEventWhenEntityIsSaved.inner"

33.
We just have to save
class MyController
{
public function action(Request $request, $identifier)
{
// ...
if ($form->isValid()) {
$this->entityRepository->save($entity);
}
// ...
}
}

34.
Decorates all the things!

35.
What do we have?
4 Easy-to-change entity storage
4 Events dispatched regarding of the storage
implementation
4 Easy-to-turn-on-and-off actions (on events)
4 Easily testable code!

36.
Design patterns: they just
help us to enable change

37.
How to apply that...
4 Closes the door!
4 Uses final keyword
4 private properties
4 Create extension points when required
4 Prevent in case of

38.
Maintainability tips
4 Distinct features in their own namespaces
4 Interfaces' names should reflect their
responsibilities
4 Implementations' names should reflect their
distinction

39.
Thank you!
@samuelroze
birdie.care
https://joind.in/talk/ae6c3