Separation of concerns - DPC 12

Separation of Concerns

Separation of concerns About Joshua  Joshua Thijssen, NoxLogic /
Techademy  Freelance Consultant, Developer, Trainer  Development in PHP, Python, Perl, C, Java  [email protected]  @jaytaph

Separation of concerns About Stephan  Stephan Hochdörfer, bitExpert AG
 Department Manager Research Labs  enjoying PHP since 1999  [email protected]  @shochdoerfer

Separation of concerns It is what I sometimes have called
the separation of concerns, which [...] is yet the only available technique for effective ordering of one's thoughts. Edsger W. Dijkstra, "On the role of scientific thought" (1974)

Separation of concerns SoC […] is the process of breaking
a computer program into distinct features that overlap in functionality as little as possible. http://en.wikipedia.org/wiki/Separation_of_concerns

Separation of concerns It`s all about focusing!

Separation of concerns One step a time. Focus on the
details!

Separation of concerns <?php $items = array(); $token = file_get_contents("https://graph.facebook.com/oauth/access_token?...");
$feed = file_get_contents("https://graph.facebook.com/ident/feed?".$token); $feed = json_decode($feed, true); foreach($feed['data'] as $post) { if('123456789012' === $post['from']['id']) { $items[] = array( 'date' => strtotime($post['created_time']), 'message' => $post['message']); } } $feed = file_get_contents("http://search.twitter.com/search.json?q=from:ident"); $feed = json_decode($feed, true); foreach($feed['results'] as $tweet) { $items[] = array( 'date' => strtotime($tweet['created_at']), 'message' => $tweet['text']); } foreach($items as $item) { echo $item['message']; }

$feed = file_get_contents("https://graph.facebook.com/ident/feed?".$token); $feed = json_decode($feed, true); foreach($feed['data'] as $post) { if('123456789012' === $post['from']['id']) { $items[] = array( 'date' => strtotime($post['created_time']), 'message' => $post['message']); } } $feed = file_get_contents("http://search.twitter.com/search.json?q=from:ident"); $feed = json_decode($feed, true); foreach($feed['results'] as $tweet) { $items[] = array( 'date' => strtotime($tweet['created_at']), 'message' => $tweet['text']); } foreach($items as $item) { echo $item['message']; }} Controller part!

$feed = file_get_contents("https://graph.facebook.com/ident/feed?".$token); $feed = json_decode($feed, true); foreach($feed['data'] as $post) { if('123456789012' === $post['from']['id']) { $items[] = array( 'date' => strtotime($post['created_time']), 'message' => $post['message']); } } $feed = file_get_contents("http://search.twitter.com/search.json?q=from:ident"); $feed = json_decode($feed, true); foreach($feed['results'] as $tweet) { $items[] = array( 'date' => strtotime($tweet['created_at']), 'message' => $tweet['text']); } foreach($items as $item) { echo $item['message']; } View part!

Separation of concerns Very unstable. Not safe for changes....

Separation of concerns „Make everything as simple as possible...“

Separation of concerns Establish boundaries

Separation of concerns What are the boundaries? Presentation Layer

Separation of concerns What are the boundaries? Presentation Layer Business
Layer

Separation of concerns What are the boundaries? Presentation Layer Business
Layer Resource Access Layer

Isolate functionality, break it apart! Separation of concerns

Separation of concerns <?php namespace Acme\DemoBundle\Controller; use Symfony\Bundle\FrameworkBundle\Controller\Controller; use Sensio\Bundle\FrameworkExtraBundle\Configuration\Route;
use Sensio\Bundle\FrameworkExtraBundle\Configuration\Template; class DemoController extends Controller { /** * @Route("/", name="_demo") * @Template() */ public function indexAction() { $items = array(); $token = file_get_contents("https://graph.facebook.com/oauth/access_to..."); $feed = file_get_contents("https://graph.facebook.com/ident/feed?".$token); $feed = json_decode($feed, true); foreach($feed['data'] as $post) { if('123456789012' === $post['from']['id']) { $items[] = array( 'date' => strtotime($post['created_time']), 'message' => $post['message']); } }

Separation of concerns $feed = file_get_contents("http://search.twitter.com/search.json?..."); $feed = json_decode($feed, true);
foreach($feed['results'] as $tweet) { $items[] = array( 'date' => strtotime($tweet['created_at']), 'message' => $tweet['text']); } return array('items' => $items); } }

Focus on one responsibility a time! Separation of concerns

use Sensio\Bundle\FrameworkExtraBundle\Configuration\Template; class DemoController extends Controller { /** * @Route("/", name="_demo") * @Template() */ public function indexAction() { $items = array(); $token = file_get_contents("https://graph.facebook.com/oauth/access_to..."); $feed = file_get_contents("https://graph.facebook.com/ident/feed?".$token); $feed = json_decode($feed, true); foreach($feed['data'] as $post) { if('123456789012' === $post['from']['id']) { $items[] = array( 'date' => strtotime($post['created_time']), 'message' => $post['message']); } } Facebook connector

Separation of concerns $feed = file_get_contents("http://search.twitter.com/search.json?..." ); $feed = json_decode($feed,
true); foreach($feed['results'] as $tweet) { $items[] = array( 'date' => strtotime($tweet['created_at']), 'message' => $tweet['text']); } return array('items' => $items); } } Twitter connector

Interfaces as a contract Separation of concerns

Separation of concerns <?php interface ConnectorInterface { /** * Will
return an array of the latest posts. * return array */ public function getLatestPosts() { } }

Separation of concerns <?php class FacebookConnector implements ConnectorInterface { protected
$handle; public function __construct($handle) { $this->handle = $handle; } public function getLatestPosts() { $items = array(); $token = file_get_contents("https://graph.facebook.com/oauth/access..."); $feed = file_get_contents("https://graph.facebook.com/. $this->handle."/feed?".$token); $feed = json_decode($feed, true); foreach($feed['data'] as $post) { if('123456789012' === $post['from']['id']) { $items[] = array( 'date' => strtotime($post['created_time']), 'message' => $post['message']); } } return $items; } }

Separation of concerns <?php class FacebookConnector implements ConnectorInterface { protected
$handle; public function __construct($handle) { $this->handle = $handle; } public function getLatestPosts() { $token = $this->getAccessToken(); return $this->readPosts($token); } protected function getAccessToken() { return file_get_contents("https://graph.facebook.com/oauth/access_?..."); } protected function readPosts($token) { // read the post, filter all relevant and return them... } }

Separation of concerns <?php class FacebookConnectorV2 extends FacebookConnector { protected
function getAccessToken() { return md5($this->handle); } } Easy to extend, will not influence the behaviour of other methods!

use Sensio\Bundle\FrameworkExtraBundle\Configuration\Template; class DemoController extends Controller { /** * @Route("/", name="_demo") * @Template() */ public function indexAction() { $items = array(); $fb = $this->get('FbConnector'); $items += $fb->getLatestPosts(); $feed = file_get_contents("http://search.twitter.com/search.json?..."); $feed = json_decode($feed, true); foreach($feed['results'] as $tweet) { $items[] = array( 'date' => strtotime($tweet['created_at']), 'message' => $tweet['text']); }

use Sensio\Bundle\FrameworkExtraBundle\Configuration\Template; class DemoController extends Controller { /** * @Route("/", name="_demo") * @Template() */ public function indexAction() { $items = array(); $fb = $this->get('FbConnector'); $items += $fb->getLatestPosts(); $twitter = $this->get('TwitterConnector'); $items += $twitter->getLatestPosts(); return array('items' => $items); } }

Will improve the testability! Separation of concerns

Will reduce tight coupling! Separation of concerns

Will increase component reuse! Separation of concerns

The value of separation Why should I do it? Separation
of concerns

The value of separation 1. Getting rid of code duplication
Separation of concerns

The value of separation 2. Application becomes more stable and
easier to understand Separation of concerns

The value of separation 3. Single responsibility offers clear extension
points Separation of concerns

The value of separation 4. Increases the reusability of components

Separation of concerns How to separate the concerns?

Separation of concerns How to separate? Horizontal Separation Presentation Layer
Business Layer Resource Access Layer

Separation of concerns How to separate? Service Separation Service Interface
Layer Business Layer Resource Access Layer

Separation of concerns How to separate? Service Separation Frontend /
UI Webservers REST API Datastore Solr Search Service

Separation of concerns How to separate? Vertical Separation Module A
Module B Module C

Separation of concerns How to separate? Vertical Separation Presentation Layer
Business Layer Resource Access Layer Presentation Layer Business Layer Resource Access Layer Presentation Layer Business Layer Resource Access Layer

Cross-cutting concerns? How to deal with security or logging aspects?

Separation of concerns How to separate? Aspect Separation Presentation Layer
Business Layer Resource Access Layer Aspects

Separation of concerns How to separate? Aspect Separation <?php namespace
Acme\Products\Aspects; /** * @FLOW3\Aspect */ class LoggingAspect { /** * @FLOW3\Inject * @var \Acme\Logger\LoggerInterface */ protected $logger; /** * @param \TYPO3\FLOW3\AOP\JoinPointInterface $joinPoint * @FLOW3\Before("method(Acme\Products\Model\Product->delete())") */ public function log(\TYPO3\FLOW3\AOP\JoinPointInterface $jp) { $product = $jp->getMethodArgument('product'); $this->logger->info('Removing ' . $product->getName()); } }

Separation of concerns Dependency Direction

Separation of concerns Dependency Direction "High-level modules should not depend
on low-level modules. Both should depend on abstractions." Robert C. Martin

Separation of concerns Inverting Concerns Presentation Layer Business Layer Resource
Access Layer

Separation of concerns Inverting Concerns Presentation Layer Business Layer Resource
Access Layer Presentation Layer Business Layer Resource Access Layer UI Component

Separation of concerns Inverting Concerns The goal of Dependency Injection
is to separate the concerns of obtaining the dependencies from the core concerns of a component.

Separation of concerns What are the benefits? Let`s recap....

Separation of concerns What are the benefits? 1. Facilitate reusability

Separation of concerns What are the benefits? 2. Ensure the
maintainability

Separation of concerns What are the benefits? 3. Increasing the
code quality

Separation of concerns What are the benefits? 4. Enables everyone
to understand the application

Separation of concerns What are the benefits? 5. Allows developers
to work on components in isolation

Thank you!

http://joind.in/6244

Separation of concerns - DPC 12

Separation of concerns - DPC 12

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