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ZF2 Modules and Services (And DI)Maurice Kherlakian

Zend Technologies


Who am I?

• Zend Professional Services consultant

• Worked with PHP for about 10 years

• Based in Montreal

2 Zend Professional Services

Linkedin: http://ca.linkedin.com/in/mkherlakian

Twitter: http://twitter.com/mkherlakian

Email: [email protected]

http://ca.linkedin.com/in/mkherlakian

http://twitter.com/mkherlakian

mailto:[email protected]


ZF2 Modules – What are they?

• Discrete blocks of code

• Allow for code re-use (not only within ZF2 but with other frameworks – Sf2 anyone?)

• Physically a namespaced directory

• If written well, distributable and re-usable

• Examples: User module (authentication – login/logout…)

ACL module

Blog module



Why are they better than ZF1’s modules

• ZF1 modules had serious problems

• Tightly coupled with MVC

• Could not be easily reused

• Bootstrapping expensive

• Not self-contained

• No dependency management


ZF2 addresses all of these problems


Requirements for a module – Module class

• A namespaced class called Module


<?php

namespace Mymod;class Module {}

• That’s it!


Requirements for a module – Directory structure

• There is, of course, a recommended directory structure



Requirements for a module - Registration

• In order for the application (Zend/Application) to run your module, it has to be registered


<?php //application.config.php

return array( 'modules' => array( //Which modules are we loading? 'Application', 'Mymod', ), 'module_listener_options' => array( 'config_glob_paths' => array( 'config/autoload/{,*.}{global,local}.php', ), 'config_cache_enabled' => false, 'cache_dir' => 'data/cache', 'module_paths' => array( //What paths are we loading modules from? './module', //We will look for a Module.php file in subdirs './vendor', //one level down from this dir *by default* ), ), 'service_manager' => array( //More on that later 'use_defaults' => true, 'factories' => array( ), ),);


Optional for a module – getConfig()• Called automatically to get the module’s configuration and

aggregate it with the other modules

• Best is to include a config file that returns a php array (best practice in ZF2 in general)


<?phpnamespace Mymod;

use Zend\ModuleManager\ModuleManager, Zend\Mvc\MvcEvent;

class Module { public function getConfig() { return include(__DIR__.'/config/module.config.php'); }}


Optional for a module – init()• A module can have an init() method that fires upon

initialization

• The ModuleManager is passed to the init function as an argument




class Module { public function init(ModuleManager $e) { $e->events()->attach( 'loadModules.post', function($e) { echo 'postLoad from MyMod'; }, 100); $e->events()->getSharedManager()->attach( __NAMESPACE__, 'dispatch', function($e) { echo "Only if dispatched to Mymod"; }, 100); }}


Optional for a module – onBootstrap()• And if init() is too early, ModuleManager automatically

registers the onBootstrap method if found in the module

• An MvcEvent is passed as the argument




class Module { public function onBootstrap(MvcEvent $e) { $request = $e->getRequest(); }}


Optional for a module – Dep solving

• Thru getProvides() and getDependencies()

• Off by default, can be turned on


<?php

namespace Blog;class Module { public function getProvides() { return array( 'name' => 'Blog', 'version' => '0.1.0', ); } public function getDependencies() { return array( 'php' => array( 'required' => true, 'version' => '>=5.3.1', ), 'ext/mongo' => array( 'required' => true, 'version' => '>=1.2.0', ), ); }}


ModuleManager

• It’s automatically instantiated in your Zend\Application

• It fulfills 3 functions: Aggregates enabled modules (allows you to iterate over

them)

Aggregates the configuration from each module

Triggers the module initialization

• There are many events for which the ModuleManager is passed as an argument

• This allows you to provide listeners at practically any point in the code to get access to the manager



An MVC module

• In most cases that’s what you will want


<?php //module.config.phpreturn array( 'router' => array( 'routes' => array( 'Mymod' => array( 'type' => 'Zend\Mvc\Router\Http\Literal', 'options' => array( 'route' => '/mymod', 'defaults' => array( 'controller' => 'mymod', 'action' => 'index', ), ), ), ), ), 'controller' => array( 'classes' => array( 'mymod' => 'Mymod\Controller\IndexController', ), ), 'view_manager' => array( 'template_path_stack' => array( __DIR__ . '/../view', ), ),);


The missing link - bootstrapping – index.php


<?php // /public/index.php

require_once 'Loader/StandardAutoloader.php';use Zend\Loader\StandardAutoloader, Zend\ServiceManager\ServiceManager, Zend\Mvc\Service\ServiceManagerConfiguration;

$loader = new StandardAutoloader();$loader->registerNamespace('Application', 'module/Application/src/Application');$loader->registerNamespace('Mymod', 'module/Mymod/src/Application');

spl_autoload_register(array($loader, 'autoload'));

// Get application stack configurationchdir(dirname(__DIR__));$configuration = include 'config/application.config.php';

// Setup service manager$serviceManager = new ServiceManager(new ServiceManagerConfiguration($configuration['service_manager']));$serviceManager->setService('ApplicationConfiguration', $configuration);$serviceManager->get('ModuleManager')->loadModules();

// Run application$serviceManager->get('Application')->bootstrap()->run()->send();


The missing link - bootstrapping – index.php


• Autoloading – it is the responsibility of index.php to set up autoloading

• This is because modules have to be portable between different frameworks (reusability)

• Any PSR-0 autoloader should work, it does not have to be ZF2’s autoloader For example Rob Allen’s Skeleton module uses Composer’s autoloader

• The next lines are the ServiceManager’s setup (more on it later)

https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-0.md

http://akrabat.com/zend-framework-2-tutorial/


Modules distribution

• Any source you can think of Pyrus

Git

Http

Tar & send

Composer

• There is already a ZF2 modules site

http://modules.zendframework.com/

(We need help! Want to contribute?)





Modules packaging

• Tar/Zip

• Phar (being careful that writes occur in location external to the archive)



Location, location, locationDI - short summary

• Since the presentation was originally about Zend\Di it’s only fair that we talk about it!

• DI is the practice of reducing coupling between classes by injecting dependent classes in the subject instead of instantiating them


<?php //No DIclass DbAdapter { public function __construct($host, $user, $pass, $db) { //... }}

class Author { protected $_db; public function __construct($host, $user, $pass, $db) { $this->_db = new DbAdapter($host, $user, $pass, $db); }}




<?php //DIclass DbAdapter { public function __construct($host, $user, $pass, $db) { //... }}

class Author { protected $_db; public function __construct($db) { $this->_db = $db; }}

$db = new DbAdapter();$author = new Author($db);

• That’s all it is – Really! Makes it easy to substitute the DB class for mocking, or to change it all together for instance, and promotes decoupling and reusability. The D in SOLID.




<?php

$db = new DbAdapter();$gateway = new DbGateway($db);$cache = new Cache();$log = new Log();

$author = new Author($db, $gateway, $cache, $log);$authors = $author->fetchAll();

• Consider the case that an Author needs a DbGateway, which needs a DbAdapter, and a logging and caching class

• 5 lines of code for initialization, but only one line for what we really need to do. Lots of boilerplate code

• Enter Dependency Injection Containers, or DiC – Zend\Di is one of them, so is the Symfony DiC, and a number of others

https://github.com/symfony/DependencyInjection




Location, location, locationDiC – Zend\Di\Di()


<?php

$config = array( 'instance' => array( 'Author' => array( 'parameters' => array( 'gateway' => 'DbGateway', 'cache' => 'Cache', 'log' => 'Log' ) ), 'DbGateway' => array( 'parameters' => array( 'db' => 'DbAdapter', ) ), 'DbAdapter' => array( 'parameters' => array( 'host' => 'somehost', 'user' => 'someuser', 'pass' => 'somepass', 'db' => ‘somedb' ) ), 'Cache' => array( ), 'Log' => array( ) ) );

$di = new Zend\Di\Di();$di->configure(new Zend\Di\Configuration($config));

$author = $di->get('Author');


Location, location, locationDiC – Zend\Di\Di()

• The last line on the previous slide:

$author = $di->get('Author');

Returns a fully configured Author object, following the definition we provided

• DiC does instantiation and auto-wiring

• Zend\Di, although difficult to show here, is a complex solution for complex problems – it can easily be abused

• For simpler problems, and more in line with the PHP philosophy, ServiceManager replaced it



Location, location, locationLocation v/s Injection

• Service manager is a ServiceLocator !== DiC

• BUT DiC === Service Locator

• One main difference is that the subject requiring the dependencies is: Not aware of the DiC when using DI (the dependency is injected)

Is aware of the locator in the case of SL, and asks the locator to obtain the dependency

• ServiceManager is a service locator

Think back to index.php:

$serviceManager->get('ModuleManager')->loadModules();

• Martin Fowler is the subject matter expert on this: http://martinfowler.com/articles/injection.html


http://martinfowler.com/articles/injection.html

http://martinfowler.com/articles/injection.html


Location, location, location Zend\ServiceManager\ServiceManager()

• Service manager uses factories to generate its services

• Factory can be a class implementing Zend\ServiceManager\FactoryInterface or a php closure



Location, location, locationZend\ServiceManager\ServiceManager()


<?phpclass ServiceConfiguration extends Configuration{ public function configureServiceManager(ServiceManager $serviceManager) { $serviceManager->setFactory('author', function(ServiceManager $sm) { $dbGateway = $sm->get('db_gateway'); $cache = $sm->get('cache'); $log = $sm->get('log'); return new Author($dbGateway, $cache, $log); } ); $serviceManager->setShared('author', false); $serviceManager->setFactory('db_gateway', function(ServiceManager $sm){ $dbAdapter = $sm->get('db_adapter'); return new DbGateway($dbAdapter); } ); $serviceManager->setFactory('db_adapter', function(ServiceManager $sm) { //Using hard-coded values for the example, but normally you would either create a factory //and inject the values from a config file //or get the configuration from the ServiceManager and read the valuees in return new DbAdapter('somehost', 'someuser', 'somepass', 'somedb'); } ); $serviceManager->setFactory('cache', function(ServiceManager $sm) { return new Cache(); } ); $serviceManager->setFactory('log', function(ServiceManager $sm) { return new Log(); } ); }}

$config = new ServiceConfiguration();$sm = new ServiceManager();$config->configureServiceManager($sm);

$author = $sm->get('author');



• The example above purposely uses closures to illustrate that a full-fledged factory is not needed

• But in a lot of cases, implementing a factory makes sense - rewriting DbAdapter from the above example as a factory:


<?phpuse Zend\ServiceManager\FactoryInterface;

//The factory classclass AuthorFactory implements FactoryInterface { public function createService(Zend\ServiceManager\ServiceLocatorInterface $sl) { $dbGateway = $sl->get('db_gateway'); $cache = $sl->get('cache'); $log = $sl->get('log'); return new Author($dbGateway, $cache, $log); }}

//And the configuration classclass ServiceConfiguration extends Configuration{ public function configureServiceManager(ServiceManager $serviceManager) { //... $serviceManager->setFactory('author', 'AuthorFactory'); //... }}



• The example above purposely uses closures to illustrate that a full-fledged factory is not needed

• But in a lot of cases, implementing a factory makes sense - rewriting DbAdapter form the above example as a factory:


<?phpuse Zend\ServiceManager\FactoryInterface;

//The factory classclass AuthorFactory implements FactoryInterface { public function createService(Zend\ServiceManager\ServiceLocatorInterface $sl) { $dbGateway = $sl->get('db_gateway'); $cache = $sl->get('cache'); $log = $sl->get('log'); return new Author($dbGateway, $cache, $log); }}

//And the configuration classclass ServiceConfiguration extends Configuration{ public function configureServiceManager(ServiceManager $serviceManager) { //... $serviceManager->setFactory('author', 'AuthorFactory'); //... }}


Location, location, locationSetting and retrieving the locator

• In most MVC components (e.g.Controllers) the ServiceManager component is composed automatically by the MVC stack

• The interface Zend\ServiceManager\ServiceLocatorAwareInterface can be implemented to ensure that a service locator is composed in the subject class

• Two methods, SetServiceLocator(ServiceLocatorInterface $locator) and getServiceLocator() must be implemented

• Notice that the Component is ServiceManager(), but the interface is ServiceLocatorInterface. This is to allow you to provide an alternative implementation of service locator.



Location, location, locationSetting and retrieving the locator

• Controllers implement ServiceLocatorAwareInterface therefore


<?php

namespace Mymod\Controller;

use Zend\Mvc\Controller\ActionController, Zend\View\Model\ViewModel;

class IndexController extends ActionController{ public function indexAction() { $sl = $this->getServiceLocator(); $sl->get('author'); return new ViewModel(); }}


Locating the injector or injecting the locator?

• Although ServiceManager is now the goto dependency management component in ZF2, Di actually still exists as a fallback (by default)

• One can specify a collection AbstractFactories to ServiceManager on which it will fall back if it does not find the target class

• Therefore, Zend\ServiceManager\Di\DiAbstractFactory is an abstract factory to which the name of the object is passed if it is not found by ServiceManager (the order can be changed)

• You can also, of course, provide your own service factory (Proxy class to other frameworks maybe?)



Some references

• ZF2 module site: http://modules.zendframework.com/

• Rob Allen’s Skeleton: https://github.com/zendframework/ZendSkeletonApplication

• Matthew’s discussion on Modules: http://mwop.net/blog/267-Getting-started-writing-ZF2-modules.html

• Ralph on the decisions that drove to ServiceManager: http://zend-framework-community.634137.n4.nabble.com/Services-Instances-Dependencies-in-ZF2-td4584632.html

• SOLID OO design: http://en.wikipedia.org/wiki/SOLID_(object-oriented_design)




https://github.com/zendframework/ZendSkeletonApplication

https://github.com/zendframework/ZendSkeletonApplication

http://mwop.net/blog/267-Getting-started-writing-ZF2-modules.html

http://mwop.net/blog/267-Getting-started-writing-ZF2-modules.html

http://zend-framework-community.634137.n4.nabble.com/Services-Instances-Dependencies-in-ZF2-td4584632.html



http://en.wikipedia.org/wiki/SOLID_(object-oriented_design


• Download ZF2 and happy coding!

http://zendframework.com/zf2

Thank You!






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