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BUILDING
THE
TIMELESS WAY
OF
John Athayde
RUBYNATION MAY 2013
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I’m Jean Valjean.
WHO AM I?
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Get our bearings here...
WHAT WE’RE
GONNA COVER
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PATTERNS
ARCHITECTURE
PATTERN LANGUAGES & HISTORY
ANTI-PATTERNS
APPLY some THEORY
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LET’S GET ON THE SAME PAGE
“PATTERNS”
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A design pattern systematically names,
motivates, and explains a general design that
addresses a recurring design problem in
object-oriented systems.
It describes the problem, the solution, when to
apply the solution, and its consequences.
It also gives implementation hints and examples.
The solution is a general arrangement of
objects and classes that solve the problem. The
solution is customized and implemented to solve
the problem in a particular context.
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1
3
2
4 DESIGN
PATTERNS
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1PATTERN NAME
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2 The Problem
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3The solution
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4consequences
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“Design patterns help you identify
less-obvious abstractions and the
objects than can capture them. For
example, objects that represent a
process or algorithm don’t occur in
nature, yet they are a crucial part of
flexible designs.”
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Iterator Pattern
Iterate over elements of a collection without exposing the internals...
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.each
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Patterns?
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The Three-book series
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“How can you distribute responsibility for
design through all levels of a large hierarchy,
while still maintaining consistency and
harmony of overall design?”
— M. J. Dominus 2002
ALEXANDER’S QUEST:
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PRINCIPLES
ARE PATTERNS
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DRY
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YAGNI
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SRP
SINGLE RESPONSIBILITY PRINCIPLE
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OCP
OPEN/CLOSED PRINCIPLE
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LSP
LISKOV SUBSTITUTION PRINCIPLE
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ISP
INTERFACE SEGREGATION PRINCIPLE
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DIP
Dependency inversion PRINCIPLE
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S O L I D
SRP OCP LSP ISP DIP
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WHERE DID PATTERNS COME FROM?
ARCHITECTURE
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WORKING WITHIN
THE LANGUAGE
OF CLASSICAL
ARCHITECTURE.
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http://www.flickr.com/photos/cindy47452/3682879190/
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crafstmen
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ENGINEERS
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architects
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BUILDERS
W E F A N C Y O U R S E L V E S
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“Engineers frequently have to make decisions
of great practical consequence in the face of
incomplete and uncertain knowledge.”
— Walter Vincenti
ON ENGINEERS:
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PROBLEM:
too many people think that
“design patterns” in software
means a library of Code templates.
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http://www.patterntap.com
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“
design patterns are
suggested approaches
seen in the wild.
- B R I A N H O G A N
”
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STRIVING
SO
WHAT ARE WE
TOWARDS?
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HAS NO NAME
THE
QUALITY
OF A SPACE
that
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Gibellina, Italy
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Gibellina Nuova, Italy
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Welcome to negative town.
ANTIPATTERNS
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D
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2
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Gibellina Nuova, Italy
D
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“Big Ball of Mud” Paper (aka Shanty Towns)
D
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D
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Walking the Tree
D
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Inheritance
Everywhere
D
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2
COMPOSITION
DELEGATE
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@account.customer.address.state
D
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class Customer < ActiveRecord::Base
has_one :address
has_one :account
...
def state
address.state
end
...
end
@account.customer_state
2
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FAT Models
D
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MODULES
CONCERNS
PLUGINS*
GEMS
ENGINES
2
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CALLBACKS
before_validation
before_validation on: :create
after_validation
after_validation on: :create
before_save
before_create
after_create
after_save
2
D
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RAILS IS A SERIES OF
VERY LARGE TUBES
LIBRARIES
2
D
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class RemoteProcess < ActiveRecord::Base
scope :running, where(:state => ‘Running’)
scope :system, where(:owner => [‘root’, ‘mysql’])
scope :sorted, order(“percent_cpy desc”)
scope :top, lamda {|1| limit(1)}
end
RemoteProcess.running.sorted.top(10)
RemoteProcess.running.system.sorted.top(5)
sample from Rails Antipatterns pp 37
2
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rails g model {modelname}
D
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DSL
ALL THE THINGS
D
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DIV-itis
PHP-itis
Java-isms
D
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2
TYPOGRAPHIC
REFACTORING
http://naildrivin5.com/blog/2013/05/17/source-code-typography.html
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M V C
2
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<% if location.present? %> Located in <%= @client.location %> <% else %> Location Unknown <% end %>
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Untested Code
D
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FAT Controllers
ONE CONTROLLER TO RULE THEM ALL... or not.
D
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So what do we do?
THE KERNEL
OF THE WAY
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“
design patterns are
suggested approaches
seen in the wild.
- B R I A N H O G A N
”
T H I S B E A R S R E P E A T I N G :
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“The best way to learn to write simple code is
to write simple code! Patterns, like all forms
of complexity, should be avoided until they
are absolutely necessary. That’s the first thing
beginners need to learn. Not the last thing. ”
— Je Atwood c. 2005
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“
You cannot say that you are
correctly applying a design
pattern unless you are
confronting the problem
that the pattern is supposed
to solve
– R U S S O L S O N
”
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“...mediocre developers never even ask why.
They just arrive at the first solution that
works and keep plowing ahead.”
— Je Atwood, c.2005
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PATTERNS
THEREFORE
REMEMBER
THAT IT’S NOT ABOUT USING
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LANGUAGE
it’s about
speaking a
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Let’s go theory!
AND YET...
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HAS NO NAME
THE
QUALITY
OF A SPACE
that
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“Indeed this ageless character has nothing, in
the end, to do with languages.
The language, and the processes which stem
from it, merely release the fundamental order
which is native to us.”
— The Timeless Way of Building, Chapter 27
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“They do not teach us, they only remind us of
what we know already, and of what we shall
discover time and time again, when we give
up our opinions, and do exactly what emerges
from ourselves.”
— The Timeless Way of Building, Chapter 27
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“To make a building egoless, the builder must
let go of all his willful images, and start with a
void.
You are able to do this only when you no
longer fear that nothing will happen, and you
can therefore afford to let go of your images.
At this stage, the building’s life will come
directly from your language.”
— The Timeless Way of Building, Chapter 27
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“Yet , at the very moment when you first
relax, and let the language generate the
buildings in your mind, you will begin to see
how limited your language is.
One place can have good patterns in it and be
dead.
Another place can be without the patterns
which apply to it, and yet still be alive. ”
— The Timeless Way of Building, Chapter 27
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“The pattern ALCOVE–which first
functioned as an intellectual crutch–is no
longer necessary to you.
You see reality directly, like an animal.
You make the alcove as an animal might
make an alcove–not because of the concept–
but directly, simply because it is appropriate.”
— The Timeless Way of Building, Chapter 27
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The Three-book series
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@boboroshi | @therailsview
THANK YOU
AthaydeWilliamsRailsView
BOOK CODE FOR 25% OFF
AT www.pragprog.com/titles/warv:
[email protected]
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