Adding Dependency Injection to Legacy Applications

DependencyAddingInjection To Legacy Applications

Who Is i3logix?

Inversion of Control

Dependency Injection

Built-InFlexibility

interface Calc { public function __invoke($left, $right);}class AddCalc implements Calc { public function __invoke($left, $right) { return $left + $right; }}class SubCalc implements Calc { public function __invoke($left, $right) { return $left - $right; }}

class Calculator{ public function __invoke(Calc $calc, $left, $right){ return $calc($left, $right); }}$calculator = new Calculator();echo $calculator(new AddCalc(), 2, 1), "n";echo $calculator(new SubCalc(), 2, 1), "n";

De-Coupling

Have Clear Goals

It’sonly aTool

I TN EJ C HE NC IT QI UO EN S

class Status { public function get($system) { $client = new Zend_Http_Client(); $r = $client->setUri(SERVICE_URI) ->setParameterGet(compact(system)) ->request(GET); if ($r->isSuccessful()) { return $r->getBody(); } return false; }}

Constructor Injection Vs.Setter/Property Injection

class StatusSetterInject{ protected $client; public function setClient(Zend_Http_Client $client){ $this->client = $client; } public function get($system){ $r = $this->client->setUri(SERVICE_URI) ->setParameterGet(compact(system)) ->request(GET); if ($r->isSuccessful()){ return $r->getBody(); } return false; }}

class StatusConstructInject{ protected $client; public function __construct(Zend_Http_Client $client){ $this->client = $client; } public function get($system){ $r = $this->client->setUri(SERVICE_URI) ->setParameterGet(compact(system)) ->request(GET); if($r->isSuccessful()){ return $r->getBody(); } return false; }}

Init Pattern

class StatusInit{ protected $client; public function __construct(Zend_Http_Client $client){ $this->client = $client; $this->init(); } public function init(){ //Left empty } public function get($system){ $r = $this->client->setUri(SERVICE_URI) ->setParameterGet(compact(system)) ->request(GET);//... }}

OptionalInjection

class StatusConstructInjectOptional{ protected $client; public function __construct( Zend_Http_Client $client = null){ if($client === null){ $client = new Zend_Http_Client(); } $this->client = $client; } public function get($system){ $r = $this->client->setUri(SERVICE_URI) ->setParameterGet(compact(system)) ->request(GET);//... }}

class StatusSetterInjectOptional{ protected $client; public function setClient(Zend_Http_Client $client){ $this->client = $client; } protected function getClient(){ if ($this->client === null){ $this->client = new Zend_Http_Client(); } return $this->client; } public function get($system){ $r = $this->getClient()->setUri(SERVICE_URI) ->setParameterGet(compact(system)) ->request(GET);//...

Class Name Override

class StatusClassNameOverrideConstruct{ protected $clientClass; public function __construct($class = Zend_Http_Client){ $this->clientClass = $class; } public function get($system){ $client = new $this->clientClass; $r = $this->getClient()->setUri(SERVICE_URI) ->setParameterGet(compact(system)) ->request(GET); if($r->isSuccessful()){ return $r->getBody(); } return false; }}

class StatusClassNameOverrideSetter{ protected $clientClass = Zend_Http_Client; public function setClass($class){ $this->clientClass = $class; } public function get($system){ $client = new $this->clientClass; $r = $this->getClient()->setUri(SERVICE_URI) ->setParameterGet(compact(system)) ->request(GET); if($r->isSuccessful()){ return $r->getBody(); } return false; }}

BUT I NEED TO CREATE OBJECTS?

class PolyBad { public function foo($bar) { if (get_class($bar) === SomeOtherClass) { $tmp = new SomeClass(); } }}

class PolyGood { public function foo(SomeClass $bar) { if ($baz instanceof SomeInterface) { // Do something } }}

class Factory{ public function create(){ return new SimpleClass(); }}

Dynamic Factory

abstract class FactoryAbstract{ protected abstract function getClassName(); public function create(){ $class = $this->getClassName(); $argList = func_get_args(); if (count($argList) < 1){ return new $class; } $rClass = new ReflectionClass($class); return $rClass->newInstanceArgs($argList); }}

WHAT IS INJECTING THESE OBJECTS?

Injector, Provider, Container

Configuration

<service id="bar" class="FooClass" shared="true" constructor="getInstance"> <file>%path%/foo.php</file> <argument>foo</argument> <argument type="service" id="foo" /> <argument type="collection"> <argument>true</argument> <argument>false</argument> </argument> <configurator function="configure" /> <call method="setBar" /> <call method="setBar"> <argument>foo</argument> <argument type="service" id="foo" /> <argument type="collection"> <argument>true</argument> <argument>false</argument> </argument> </call></service>

Interfaces

if($obj instanceof InjectDb){ $obj->setDb($this->serviceLocator->getDb());}if($obj instanceof InjectTool){ $obj->setTool($this->serviceLocator->getTool());}if($obj instanceof InjectClientBuilder){ $obj->setClientBuilder($this->getClientBuilder());}if($obj instanceof InjectEvent){ $obj->setEvent($this->serviceLocator->getEvent());}

Duck Typing

abstract class Zend_View_Abstract implements Zend_View_Interface//...public function registerHelper($helper, $name){//... if (!$helper instanceof Zend_View_Interface){ if (!method_exists($helper, $name)){ require_once Zend/View/Exception.php; $e = new Zend_View_Exception( View helper must …); $e->setView($this); throw $e; } } if (method_exists($helper, setView)){ $helper->setView($this); }//...

Auto Wiring

$rParmList = $methodReflection->getParameters();foreach($rParmList as $rParm ){ $parmClass = $rParm->getClass(); if($parmClass !== null){ $bindConfig->getInjectionConfig() ->addMethodInstanceKey( $methodName, $parmClass->getName()); }else{ throw new Exception( "Not possible to configure automatically" ); }}

Annotations

/** * @Singleton */class LoggerSimple{ /** * @Inject Zend_Db_Adapter_Abstract */ public $db; /** * @Inject * @Arg Zend_Db_Adapter_Abstract */ public function __construct($db){ $this->db = $db; } /** * @Inject * @Arg Zend_Db_Adapter_Abstract */ public function setDb($db){ $this->db = $db; }}

/** * @ImplementedBy LoggerSimple */interface Logger{ public function log($message, $level);}

$rClass = new ReflectionAnnotatedClass($config->getClass());if($rClass->isInterface()){ if($rClass->hasAnnotation(ImplementedBy) === false){ throw new Exception(…); } $impClass = $rClass->getAnnotation(ImplementedBy)->value; if($impClass === null){ throw new Exception (…); } $config->setImplementationClass($impClass);}

Combine. Win!

Singleton

class Db{ protected function __construct(){} protected function __clone(){} public static function instance(){ static $instance = null; if($instance === null){ $instance = new static(); } return $instance; }}

Singleton + Registry

class Registry{ protected static $reg = array(); public static function add($key, $value){ static::$reg[$key] = $value; } public static function get($key){ return static::$reg[$key]; }}

class Registry{ protected static $reg = array(); public static function add($key, $value){ static::$reg[$key] = $value; } public static function get($key){ $value = static::$reg[$key]; if(is_callable($value)){ return $value(); } return $value; }}

Registry::add(db, function (){return new Db();});var_dump(Registry::get(db));

Service Locator

class ServiceLocator{ protected function __construct(){} protected function __clone(){} public static function instance(){ static $instance = null; if($instance === null){ $instance = new static(); } return $instance; } public function getDb(){ static $db = null; if($db === null){ $db = new Db(); } return $db; }}

Coarse-Grained Fine-Grained

Design by Contract

class Logger{}

abstract class LoggerAbstract{}class LoggerEcho extends LoggerAbstract{}class LoggerFile extends LoggerAbstract{}

interface LoggerInterface{}abstract class LoggerAbstract implements LoggerInterface{}class LoggerEcho extends LoggerAbstract{}class LoggerFile extends LoggerAbstract{}class LoggerOddBall implements LoggerInterface{}

class Logger{}

abstract class Logger{}class LoggerEcho extends Logger{}class LoggerFile extends Logger{}

interface Logger{}abstract class LoggerAbstract implements Logger{}class LoggerEcho extends Logger{}class LoggerFile extends Logger{}class LoggerOddBall implements Logger{}

Prefer Composition Over Inheritance

WHAT’S ALREADY OUT THERE?

YOU NEED AGAME PLAN!

http://joind.in/3740T HANK Y OU!

Adding Dependency Injection to Legacy Applications

by Sam Hennessy on Oct 19, 2011

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Adding Dependency Injection to Legacy Applications — Presentation Transcript