Refactoring to Design Pa0erns Simone Carle5 phpDay 2009 – May 15‐16, 2009 – Verona, Italy h0p://grusp.it ‐ h0p://phpday.it ‐ h0p://joind.in/event/view/34

About Me •  Technical Manager in Altura Labs •  Addicted to Agile Development •  Fallen in love with Development Best Prac=ces •  Passionate about Object Oriented Programming phpDay 2009 – 15 e 16 Maggio Verona, Italy

Designing object oriented soKware is hard, and designing reusable object‐oriented soKware is even harder. Design Pa*erns (GoF) phpDay 2009 – 15 e 16 Maggio Verona, Italy

EvoluRon

Maintainability phpDay 2009 – 15 e 16 Maggio Verona, Italy

Maintainability Long project lifecycle phpDay 2009 – 15 e 16 Maggio Verona, Italy

Maintainability Long project lifecycle Scalability phpDay 2009 – 15 e 16 Maggio Verona, Italy

Maintainability Long project lifecycle Scalability Flexibility phpDay 2009 – 15 e 16 Maggio Verona, Italy

… and we need it for yesterday! phpDay 2009 – 15 e 16 Maggio Verona, Italy

Design for Changes The key to maximizing reuse lies in an=cipa=ng new requirements and changes to exis=ng requirements, and design your system so that they can evolve accordingly. Design Pa*erns (GoF) phpDay 2009 – 15 e 16 Maggio Verona, Italy

No content

Bad Smell hVp://www.codinghorror.com/blog/ archives/000589.html

D.R.Y. Don’t repeat yourself

K.I.S.S. Keep it Simple, Stupid

Y.A.G.N.I. You Ain't Gonna Need It

Over‐Engineering phpDay 2009 – 15 e 16 Maggio Verona, Italy

Under‐Engineering phpDay 2009 – 15 e 16 Maggio Verona, Italy

Refactoring

phpDay 2009 – 15 e 16 Maggio Verona, Italy

What is Refactoring? Refactoring is a disciplined technique for restructuring an exis=ng body of code, altering its internal structure without changing its external behavior. Mar2n Fowler phpDay 2009 – 15 e 16 Maggio Verona, Italy

Why? •  Improve readability •  Improve maintainability •  Gain a beVer understanding of code phpDay 2009 – 15 e 16 Maggio Verona, Italy

How? •  Small steps •  Con=nuous •  Don’t add features •  … or bugs •  Have a good knowledge of the code phpDay 2009 – 15 e 16 Maggio Verona, Italy

Design Pa0erns

Design PaVerns describe simple and elegant solu=ons to specific problems in object oriented soKware design. phpDay 2009 – 15 e 16 Maggio Verona, Italy

phpDay 2009 – 15 e 16 Maggio Verona, Italy

Each paVerns describes a problem which occurs over and over again in our environment, and then describes the core of the solu=on to that problem, in such a way that you can use this solu=on a million =mes over. Christopher Alexander phpDay 2009 – 15 e 16 Maggio Verona, Italy

Context Problem Solu=on phpDay 2009 – 15 e 16 Maggio Verona, Italy

A word of warning Ideally when the appropriate problem comes along, you should trigger the design paVern and your problem is solved. Russ Olsen, Design Pa*erns in Ruby phpDay 2009 – 15 e 16 Maggio Verona, Italy

Design Pa0erns by Purpose •  Crea=onal PaVerns •  Structural PaVerns •  Behavioral PaVerns •  Concurrency PaVerns •  Architectural PaVerns phpDay 2009 – 15 e 16 Maggio Verona, Italy

There is a natural rela=on between paVerns and refactorings. PaVerns are where you want to be, refactorings are ways to get there from somewhere else. Mar2n Fowler phpDay 2009 – 15 e 16 Maggio Verona, Italy

TesRng

phpDay 2009 – 15 e 16 Maggio Verona, Italy

TesRng performance integra=on func=onal unit phpDay 2009 – 15 e 16 Maggio Verona, Italy

Test Driven Development phpDay 2009 – 15 e 16 Maggio Verona, Italy

Tes=ng Refactoring Design PaVerns phpDay 2009 – 15 e 16 Maggio Verona, Italy

Refactoring to Design Pa0erns

Observer

Observer The Observer paVern defines dependency between objects so that when one object change state, all its dependents are no=fied and updated automa=cally phpDay 2009 – 15 e 16 Maggio Verona, Italy

Observer Post CacheSweeper Logger EmailNo=fier phpDay 2009 – 15 e 16 Maggio Verona, Italy

Observer Post CacheSweeper Logger EmailNo=fier $post‐>=tle = “foo”; $post‐>save(); phpDay 2009 – 15 e 16 Maggio Verona, Italy

Observer Post CacheSweeper Logger EmailNo=fier $post‐>=tle = “foo”; $post‐>save(); phpDay 2009 – 15 e 16 Maggio Verona, Italy

Observer Post CacheSweeper Logger EmailNo=fier $post‐>=tle = “foo”; $post‐>save(); aKer_save() aKer_save() aKer_save() phpDay 2009 – 15 e 16 Maggio Verona, Italy

Observer Post CacheSweeper Logger EmailNo=fier $post‐>delete(); phpDay 2009 – 15 e 16 Maggio Verona, Italy

Observer Post CacheSweeper Logger EmailNo=fier $post‐>delete(); phpDay 2009 – 15 e 16 Maggio Verona, Italy

Observer Post CacheSweeper Logger EmailNo=fier aKer_delete() aKer_delete() $post‐>delete(); phpDay 2009 – 15 e 16 Maggio Verona, Italy

Code Time

Strategy

Strategy function doSomething($even, $odd) { if ($even == "secret") { if ($odd == "other secret") { return 1; } else if ("pizza" == "good") { return "Yes it is!"; } } else if ($odd != $even) { return "yeah, they are"; } else { return "I'm getting crazy"; } } phpDay 2009 – 15 e 16 Maggio Verona, Italy

Strategy method($params) { // complex logic // conditional strategy } phpDay 2009 – 15 e 16 Maggio Verona, Italy

Strategy Strategy 1 Strategy 2 Strategy 3 method($params) { $s = new Strategy(); $s->method($params); } $s = new Strategy() $s->method($params); phpDay 2009 – 15 e 16 Maggio Verona, Italy

Code Time

QuesRons? phpDay 2009 – 15 e 16 Maggio Verona, Italy

License This presenta=on is published under the AVribu=on‐Share Alike Unported Crea=ve Commons License. You are free: •  to Share — to copy, distribute and transmit the work •  to Remix — to adapt the work Under the following condi=ons: •  A0ribuRon — You must aVribute the work in the manner specified by the author or licensor (but not in any way that suggests that they endorse you or your use of the work). •  Share Alike — If you alter, transform, or build upon this work, you may distribute the resul=ng work only under the same, similar or a compa=ble license. Visit hVp://crea=vecommons.org/licenses/by‐sa/3.0/ for more details. phpDay 2009 – 15 e 16 Maggio Verona, Italy

Thank you! Slides will be available at www.simonecarleq.com www.slideshare.net/weppos Rate this talk at hVp://joind.in/talk/view/417