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

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

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

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

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

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

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

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

Observer
$post‐>delete(); Post
CacheSweeper EmailNo=fier Logger
aKer_delete() aKer_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
method($params)
{
$s = new Strategy();
$s->method($params);
}
$s = new Strategy()
Strategy 1 Strategy 2 Strategy 3
$s->method($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
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