This document provides an overview of dependency injection (DI) and aspect-oriented programming (AOP). It discusses some of the basic problems that DI and AOP aim to address, such as tight coupling between classes and cross-cutting concerns. It provides examples of implementing DI using a service container in Symfony and Google Guice-style annotations. It also demonstrates how AOP can be used for logging and caching through interceptors and pointcuts. Overall, the document introduces key concepts and patterns in DI and AOP through code examples.

1. What is this DI and AOP stuff anyway...
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2. About Me
Currently BBC Sport (Freelancer)
Lived in Japan for 15 years - love sushi
Love frameworks - not just PHP ones
Involved in Lithium and BEAR.Sunday projects
Richard McIntyre - @mackstar
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3. Dependency Injection
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4. Most Basic Example - Problem
class Mailer
{
private $transport;
public function __construct()
{
$this->transport = 'sendmail';
}
// ...
}
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5. Expensive
new Zend_Config_Ini($path, ENV);
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6. Easily becomes an inheritance mess
Sport_Lib_Builder_GenericStatsAbstract
Sport_Lib_Builder_GenericStats_Cricket_Table
Sport_Lib_Builder_GenericStats_Cricket_NarrowTable
Sport_Lib_Builder_GenericStats_CricketAbstract
Sport_Lib_API_GenericStats_Cricket
Sport_Lib_API_GenericStatsAbstract
Sport_Lib_Service_SportsData_Cricket
Sport_Lib_Service_SportsData
Sport_Lib_ServiceAbstract
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7. DI for a 5 year old
When you go and get things out of the refrigerator for yourself, you can
cause problems. You might leave the door open, you might get something
Mommy or Daddy doesn't want you to have. You might even be looking
for something we don't even have or which has expired.
What you should be doing is stating a need, "I need something to drink
with lunch," and then we will make sure you have something when you
sit down to eat.
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8. Something like this...
Application needs Foo, which needs Bar, which needs Bim, so:
Application creates Bim
Application creates Bar and gives it Bim
Application creates Foo and gives it Bar
Application calls Foo
Foo calls Bar
Bar does something
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9. The Service Container
Dependency Injection Round 1
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10. class Mailer
{
private $transport;
public function __construct($transport)
{
$this->transport = $transport;
}
// ...
}
Symfony2 Example
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11. class Mailer
{
private $transport;
public function __construct($transport)
{
$this->transport = $transport;
}
// ...
}
use SymfonyComponentDependencyInjectionContainerBuilder;
$container = new ContainerBuilder();
$container->register('mailer', 'Mailer');
Symfony2 Example
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12. class Mailer
{
private $transport;
public function __construct($transport)
{
$this->transport = $transport;
}
// ...
}
use SymfonyComponentDependencyInjectionContainerBuilder;
$container = new ContainerBuilder();
$container->register('mailer', 'Mailer');
use SymfonyComponentDependencyInjectionContainerBuilder;
$container = new ContainerBuilder();
$container
->register('mailer', 'Mailer')
->addArgument('sendmail');
Symfony2 Example
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13. class NewsletterManager
{
private $mailer;
public function __construct(Mailer $mailer)
{
$this->mailer = $mailer;
}
// ...
}
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14. class NewsletterManager
{
private $mailer;
public function __construct(Mailer $mailer)
{
$this->mailer = $mailer;
}
// ...
}
use SymfonyComponentDependencyInjectionContainerBuilder;
use SymfonyComponentDependencyInjectionReference;
$container = new ContainerBuilder();
$container->setParameter('mailer.transport', 'sendmail');
$container
->register('mailer', 'Mailer')
->addArgument('%mailer.transport%');
$container
->register('newsletter_manager', 'NewsletterManager')
->addArgument(new Reference('mailer'));
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15. use SymfonyComponentDependencyInjectionContainerBuilder;
$container = new ContainerBuilder();
$newsletterManager = $container->get('newsletter_manager');
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16. Inversion Of Control
Pattern
The control of the dependencies is inversed from one
being called to the one calling.
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17. Container
Newsletter Manager
Mailer
transport = sendmail
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18. Container
Newsletter Manager
Mailer
# src/Acme/HelloBundle/Resources/config/
services.yml
parameters:
# ...
mailer.transport: sendmail
services:
mailer:
class: Mailer
arguments: [%mailer.transport%]
newsletter_manager:
class: NewsletterManager
calls:
- [ setMailer, [ @mailer ] ]
transport = sendmail
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19. Decoupled Code
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20. Tips
Test first in isolation
Don’t need to wire together to test (Eg Environment etc)
integration tests are expensive.
When you do wire together with test/mock classes as needed
Duck Type your code / Use interfaces
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21. Friday, June 7, 13

22. $container = new Pimple();
// define some parameters
$container['cookie_name'] = 'SESSION_ID';
$container['session_storage_class'] = 'SessionStorage';
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23. $container = new Pimple();
// define some parameters
$container['cookie_name'] = 'SESSION_ID';
$container['session_storage_class'] = 'SessionStorage';
// define some objects
$container['session_storage'] = function ($c) {
return new $c['session_storage_class']($c['cookie_name']);
};
$container['session'] = function ($c) {
return new Session($c['session_storage']);
};
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24. Clever DI with Bindings
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25. Laravel 4 example
class MyConcreteClass implements MyInterface
{
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26. Laravel 4 example
class MyConcreteClass implements MyInterface
{
class MyClass
{
public function __construct(MyInterface $my_injection)
{
$this->my_injection = $my_injection;
}
}
App::bind('MyInterface', 'MyConcreteClass');
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27. Cleverer DI with Injection
Points & Bindings
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28. Google Guice
Guice alleviates the need for factories and the use of ‘new’ in
your ‘Java’a code
Think of Guice's @Inject as the new new. You will still need
to write factories in some cases, but your code will not
depend directly on them. Your code will be easier to change,
unit test and reuse in other contexts.
Ray.DI
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29. interface MailerInterface {}
PHP Google Guice Clone
Ray.DI
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30. class Mailer implements MailerInterface
{
private $transport;
/**
* @Inject
* @Named("transport_type")
*/
public function __construct($transport)
{
$this->transport = $transport;
}
}
interface MailerInterface {}
PHP Google Guice Clone
Ray.DI
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31. class Mailer implements MailerInterface
{
private $transport;
/**
* @Inject
* @Named("transport_type")
*/
public function __construct($transport)
{
$this->transport = $transport;
}
}
interface MailerInterface {}
class NewsletterManager
{
public $mailer;
/**
* @Inject
*/
public function __construct(MailerInterface $mailer)
{
$this->mailer = $mailer;
}
}
PHP Google Guice Clone
Ray.DI
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32. class NewsletterModule extends AbstractModule
{
protected function configure()
{
$this->bind()->annotatedWith('transport_type')->toInstance('sendmail');
$this->bind('MailerInterface')->to('Mailer');
}
}
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33. class NewsletterModule extends AbstractModule
{
protected function configure()
{
$this->bind()->annotatedWith('transport_type')->toInstance('sendmail');
$this->bind('MailerInterface')->to('Mailer');
}
} $di = Injector::create([new NewsletterModule]);
$newsletterManager = $di->getInstance('NewsletterManager');
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34. class NewsletterModule extends AbstractModule
{
protected function configure()
{
$this->bind()->annotatedWith('transport_type')->toInstance('sendmail');
$this->bind('MailerInterface')->to('Mailer');
}
} $di = Injector::create([new NewsletterModule]);
$newsletterManager = $di->getInstance('NewsletterManager');
$works = ($newsletterManager->mailer instanceof MailerInterface);
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35. Problems?/Gochas
1. Overly abstracted code
2. Easy to go crazy with it
3. Too many factory classes
4. Easy to loose what data is where
5. Container is like super global variable
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36. Many other
implementations
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37. Aspect Orientated
Programming
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38. The Problem
function addPost() {
$log->writeToLog("Entering addPost");
// Business Logic
$log->writeToLog("Leaving addPost");
}
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39. The Problem
function addPost() {
$log->writeToLog("Entering addPost");
// Business Logic
$log->writeToLog("Leaving addPost");
}
function addPost() {
$authentication->validateAuthentication($user);
$authorization->validateAccess($user);
// Business Logic
}
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40. Core Class Aspect Class
AOP Framework
Proxy Class
Continue Process
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41. Lithium Example -Logging in your model
namespace appmodels;
use lithiumutilcollectionFilters;
use lithiumutilLogger;
Filters::apply('appmodelsPost', 'save', function($self, $params, $chain) {
Logger::write('info', $params['data']['title']);
return $chain->next($self, $params, $chain);
});
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42. Dispatcher::applyFilter('run', function($self, $params, $chain) {
$key = md5($params['request']->url);
if($cache = Cache::read('default', $key)) {
return $cache;
}
$result = $chain->next($self, $params, $chain);
Cache::write('default', $key, $result, '+1 day');
return $result;
});
Lithium Example -Caching
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43. Friday, June 7, 13

44. Find
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45. Cache
Find
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46. Log
Cache
Find
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47. Log
Cache
Find
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48. Log
Cache
Find
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49. Log
Cache
Find
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50. Ray.AOP
Guice AOP Clone
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51. /**
* NotOnWeekends
*
* @Annotation
* @Target("METHOD")
*/
final class NotOnWeekends
{
}
Create Annotation
Create Real Class - Billing service
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52. /**
* NotOnWeekends
*
* @Annotation
* @Target("METHOD")
*/
final class NotOnWeekends
{
}
Create Annotation
class RealBillingService
{
/**
* @NotOnWeekends
*/
chargeOrder(PizzaOrder $order, CreditCard $creditCard)
{
Create Real Class - Billing service
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53. class WeekendBlocker implements MethodInterceptor
{
public function invoke(MethodInvocation $invocation)
{
$today = getdate();
if ($today['weekday'][0] === 'S') {
throw new RuntimeException(
$invocation->getMethod()->getName() . " not allowed on weekends!"
);
}
return $invocation->proceed();
}
}
Interception Logic
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54. $bind = new Bind;
$matcher = new Matcher(new Reader);
$interceptors = [new WeekendBlocker];
$pointcut = new Pointcut(
$matcher->any(),
$matcher->annotatedWith('RayAopSampleAnnotationNotOnWeekends'),
$interceptors
);
$bind->bind('RayAopSampleAnnotationRealBillingService', [$pointcut]);
$billing = new Weaver(new RealBillingService, $bind);
try {
echo $billing->chargeOrder();
} catch (RuntimeException $e) {
echo $e->getMessage() . "n";
exit(1);
}
Binding on Annotation
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55. $bind = new Bind;
$bind->bindInterceptors('chargeOrder', [new WeekendBlocker]);
$billingService = new Weaver(new RealBillingService, $bind);
try {
echo $billingService->chargeOrder();
} catch (RuntimeException $e) {
echo $e->getMessage() . "n";
exit(1);
}
Explicit Method Binding
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56. Gochas
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57. BEAR.Sunday
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