Confoo 2011 - Advanced OO Patterns

Advanced OO Patterns ConFoo 2011Tobias Schlitt <toby@qafoo.com> March 9, 2011

Advanced OO Patterns 2 / 44 Outline Introduction Lazy Initialization Dependency Injection Service Locator Data Storage

Advanced OO Patterns 3 / 44 About me Degree in computer sience More than 10 years of professional PHP Open source enthusiast Apache Zeta Components Arbit PHPUnit ...

Advanced OO Patterns 3 / 44 About me Degree in computer sience Co-Founder of More than 10 years of Qafoo GmbH professional PHP http://qafoo.com Open source enthusiast Apache Zeta Components Qafoo passion for software quality Arbit PHPUnit ...

Advanced OO Patterns 3 / 44 About me Degree in computer sience Co-Founder of More than 10 years of Qafoo GmbH professional PHP http://qafoo.com Open source enthusiast Apache Zeta Components Qafoo passion for software quality Arbit We help people to produce PHPUnit ... high quality PHP code.

Advanced OO Patterns 4 / 44 Disclaimer This talk cannot be in depth This talk shall inspire you This talk will not show UML diagrams This talk will show you quite some code This talk can seriously harm your coding habbits

Advanced OO Patterns 5 / 44 Patterns are . . . . . . universal solutions. . . . good habbits. . . . coding templates.

Advanced OO Patterns 5 / 44 Patterns are . . . . . . universal solutions. . . . good habbits. . . . coding templates. . . . names for proven ideas how a certain class of problems can be solved.

Advanced OO Patterns 6 / 44 Patterns are not . . . . . . appliable to every problem. . . . directly transferable to code. . . . always the best solution.

Advanced OO Patterns 7 / 44 Pattern classiﬁcation Creational Structural Behavioural Architectural

Advanced OO Patterns 8 / 44 Well known patterns Signal / Observer Iterator Visitor Adapter Singleton Factory

Advanced OO Patterns 10 / 44 Motivation Building a full object graph is Complex Time consuming Memory consuming Do you use all objects in every request? Idea: Initialize object when needed for the ﬁrst time

Advanced OO Patterns 11 / 44 Simple lazy initialization 1 <?php 2 3 class DatabaseInitializer 4 { 5 p r o t e c t e d $dsn ; 6 7 p r o t e c t e d $db ; 8 9 public function c o n s t r u c t ( $dsn )10 {11 $ t h i s − sn = $dsn ; >d12 }1314 p u b l i c f u n c t i o n getDatabase ()15 {16 i f ( $this− >db === n u l l )17 {18 $this− >db = new D a t a b a s e ( $ t h i s − s n ) ; >d19 }20 return $this− >db ;21 }22 }

Advanced OO Patterns 13 / 44 Goals of good OO design Modular Flexible Reusable Testable S.O.L.I.D. (http://butunclebob.com/ArticleS.UncleBob.PrinciplesOfOod)

Advanced OO Patterns 14 / 44 What’s the problem here? 1 <?php 2 3 c l a s s MessageDispatcher 4 { Inﬂexible 5 public function construct () 6 7 { $this−>m e s s e n g e r s [ ] = new Not reusable JabberMessenger () ; 8 $this−>m e s s e n g e r s [ ] = new Hardly testable MailMessenger () ; 9 }10 }1112 c l a s s MailMessenger implements Messenger13 {14 p u b l i c f u n c t i o n sendMessage ( $ t e x t )15 {16 myLogger : : g e t I n s t a n c e ( )− o g ( $ t e x t >l );17 $ t h i s − e n d M a i l ( /∗ . . . ∗/ ) ; >s18 }19 }

Advanced OO Patterns 15 / 44 Injecting dependencies 1 <?php 2 3 $ m e s s e n g e r = new M e s s a g e D i s p a t c h e r ( 4 array ( 5 new J a b b e r M e s s e n g e r ( ’ j a b b e r . e x a m p l e . o r g ’ , ’ u s e r ’ , ’ p a s s ’ ) , 6 new M a i l M e s s e n g e r ( 7 new M a i l S m t p T r a n s p o r t ( ’ m a i l . e x a m p l e . o r g ’ , ’ u s e r ’ , ’ p a s s ’ ) , 8 $ l o g g e r = new L o g g e r ( 9 new L o g g i n g D i s p a t c h e r (10 array (11 new S y s l o g L o g g e r ( ) ,12 new F i l e S y s t e m L o g g e r ( ’ l o g / e r r o r s . l o g ’ )13 )14 )15 )16 )17 ),18 $logger19 );

Advanced OO Patterns 16 / 44 What is desired? Don’t have ctors all over the place Manage dependencies Replace dependencies ﬁne grained Lazy initialization

Advanced OO Patterns 17 / 44 The Arbit DIC Exemplary for a high-end DIC Shared objects (initialized once) Closures for lazy initialization Inherent dependency resolution Base class for custom DICs Heavy use of interceptors No implementation details, see here: http://bit.ly/arbitDIC

Advanced OO Patterns 18 / 44 Managing dependencies 3 c l a s s arbitEnvironmentDIC extends arbitDependencyInjectionContainer 4 {13 public function i n i t i a l i z e ()14 {38 }39 }

Advanced OO Patterns 19 / 44 Managing dependencies 3 c l a s s arbitEnvironmentDIC extends arbitDependencyInjectionContainer 4 {13 public function i n i t i a l i z e ()14 {15 $this− ache = f u n c t i o n ( $dic ) >c16 {17 r e t u r n new a r b i t F i l e s y s t e m C a c h e ( $ d i c− e q u e s t − o n t r o l l e r ) ; >r >c18 };38 }39 }

Advanced OO Patterns 20 / 44 Managing dependencies 3 c l a s s arbitEnvironmentDIC extends arbitDependencyInjectionContainer 4 {13 public function i n i t i a l i z e ()14 {20 $this− >m e s s e n g e r = f u n c t i o n ( $ d i c )21 {22 r e t u r n new a r b i t M e s s e n g e r ( a r r a y (23 ’ e m a i l ’ = $ d i c− > >m a i l M e s s e n g e r ,24 ) );25 };38 }39 }

Advanced OO Patterns 21 / 44 Managing dependencies 3 c l a s s arbitEnvironmentDIC extends arbitDependencyInjectionContainer 4 {13 public function i n i t i a l i z e ()14 {27 $this− >m a i l M e s s e n g e r = f u n c t i o n ( $ d i c )28 {29 r e t u r n new a r b i t M a i l M e s s e n g e r (30 $ d i c−>m a i l T r a n s p o r t ,31 $ d i c− o n f i g u r a t i o n − >c >main ,32 $ d i c− o n f i g u r a t i o n − r o j e c t ( $ d i c− e q u e s t − o n t r o l l e r ) , >c >p >r >c33 $ d i c− i e w s− e c o r a t o r >v >d34 );35 };38 }39 }

Advanced OO Patterns 22 / 44 Dependency Injection Approaches Constructor injection We just saw that Setter injection Use set*() Default instances? Interface injection Speciﬁc to some containers

Advanced OO Patterns 23 / 44 More about DIC Phemto - A dependency injector for PHP 5 http://phemto.sourceforge.net/ Pimple - A small PHP 5.3 dependency injection container https://github.com/fabpot/Pimple Bucket - Basic di-container for php https://github.com/troelskn/bucket Symfony Dependency Injection http://components.symfony-project.org/ dependency-injection/ Martin Fowler on Dependency Injection http://martinfowler.com/articles/injection.html

Advanced OO Patterns 25 / 44 Service Locator Object to retrieve a Service from Deliver locator instead of service directly Basically saves constructor parameters

Advanced OO Patterns 26 / 44 Service Locator 1 <?php 2 3 c l a s s MessageServiceLocator 4 { 5 public function c o n s t r u c t ( array $messengers , Logger $ l o g g e r ) 6 { /∗ . . . ∗/ } 7 8 public function getMessengers () 9 { /∗ . . . ∗/ }1011 public function getLogger ()12 { /∗ . . . ∗/ }13 }1415 c l a s s MessageDispatcher16 {17 public function construct ( MessageServiceLocator $serviceLoc )18 { /∗ . . . ∗/ }19 }2021 ?>

Advanced OO Patterns 27 / 44 Pattern purism DIC vs. Service Locator

Advanced OO Patterns 29 / 44 The situation Model (application) Storage

Advanced OO Patterns 29 / 44 The situation Model (application) Storage store restore

Advanced OO Patterns 30 / 44 Challenges Model and storage structure differ Object relational impedance mismatch Different access approaches Query language differences Storage back end might change Back ends could even be mixed ...

Advanced OO Patterns 31 / 44 Active Record 1 <?php 2 3 class Invoice extends ActiveRecord 4 { 5 protected $id ; 6 protected $positions ; 7 protected $vat ; 8 // . . . 910 public function calculateValue ()11 { /∗ b u s i n e s s l o g i c ∗/ }12 }1314 c l a s s ActiveRecord15 {16 public function i n s e r t ()17 { /∗ . . . ∗/ }18 p u b l i c f u n c t i o n update ()19 { /∗ . . . ∗/ }20 }

Advanced OO Patterns 32 / 44 Active Record Combines storage and business logic Commonly storage logic in base class Model class corresponds to database record

Advanced OO Patterns 33 / 44 Evaluation Pros Cons Very easy to use Model structure = storage Very few code to structure write Classes become complex Business logic Storage logic Broken object semantics Changes ripple over Hard to exchange storage logic Really hard to test!

Advanced OO Patterns 34 / 44 Lesson learned . . . De-couple business and storage logic!

Advanced OO Patterns 35 / 44 Row Data Gateway 1 <?php 2 3 class Invoice 4 { 5 p r o t e c t e d $data ; 6 // . . . 7 8 public function c o n s t r u c t ( InvoiceGateway $data ) 9 { $this− ata = $data ; } >d1011 public function calculateValue ()12 { /∗ b u s i n e s s l o g i c ∗/ }13 }1415 c l a s s InvoiceGateway16 {17 protected $id ;18 protected $positions ;19 protected $vat ;2021 public function i n s e r t ()22 { /∗ . . . ∗/ }23 p u b l i c f u n c t i o n update ()24 { /∗ . . . ∗/ }25 }

Advanced OO Patterns 36 / 44 Row Data Gateway Decouples storage from business logic Still convenient OO interface for storage Still some objects coupled to storage (Table Data Gateway is a somewhat similar approach)

Advanced OO Patterns 37 / 44 Evaluation Pros Cons Easy to use Some objects model DB Few code to write structure Gateways can be Changes still ripple over generated Still hard to exchange Easier to test storage logic

Advanced OO Patterns 38 / 44 Data Mapper 1 <?php 2 3 class Invoice 4 { 5 protected $positions ; 6 protected $vat ; 7 // . . . 8 9 public function calculateValue ()10 { /∗ b u s i n e s s l o g i c ∗/ }11 }1213 interface InvoiceMapper14 {15 public function store ( Invoice $invoice ) ;16 public f u n c t i o n update ( I n v o i c e $ i n v o i c e ) ;17 public f u n c t i o n f i n d B y C u s t o m e r ( Customer $ c u s t o m e r ) ;18 }1920 c l a s s DbInvoiceMapper implements InvoiceMapper21 {22 // . . .23 }2425 ?>

Advanced OO Patterns 39 / 44 Data Mapper Decouple storage from model No OO modelling of DB structure Model does not even know a database exists

Advanced OO Patterns 40 / 44 Evaluation Pros Cons Complete decoupling Quite some code Model is not aware of storage to write Clean storage interface Mapping can Implement different storages! become complex DB changes only affect mapping layer Model changes only affect mapping layer Nice for testing

Advanced OO Patterns 41 / 44 Attribution Large parts of this talk are inspired by Patterns of Enterprise Application Architecture by Martin Fowler ISBN 978-0321127426 — http://amzn.to/PofEAA Highy recommended!

Advanced OO Patterns 42 / 44 Conclusion Patterns are not the holy grail! They assign names to good ideas They help you to talk about concepts They can inspire you

Advanced OO Patterns 43 / 44 Q/A Are there any questions left?

Advanced OO Patterns 44 / 44 Thanks for listening Please rate this talk at http://joind.in/2774 and / or give me some feedback right now!

Advanced OO Patterns 44 / 44 Thanks for listening Please rate this talk at http://joind.in/2774 and / or give me some feedback right now! This is very important for . . . Speakers Organizers You!

Advanced OO Patterns 44 / 44 Thanks for listening Please rate this talk at http://joind.in/2774 and / or give me some feedback right now! Stay in touch Tobias Schlitt toby@qafoo.com @tobySen / @qafoo Rent a PHP quality expert: http://qafoo.com

Confoo 2011 - Advanced OO Patterns

by Bachkoutou Toutou on Mar 09, 2011

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