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BUILDING
THE
TIMELESS WAY
OF
REVOLUTION CONF 2017
VIRGINIA BEACH, VIRGINIA
John Athayde @boboroshi
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I’m Jean Valjean.
WHO AM I?
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METICULOUS
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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
2
4DESIGN
PATTERNS
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1PATTERN NAME
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2THE 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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foreach
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for x in…
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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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1 3
2 4
ARCHITECTURE PATTERN:
transition space between the
street and the front door
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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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PATTERNS
ALL THE WAY
DOWN
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WHERE DO PATTERNS COME FROM?
ARCHITECTURE
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1570
ITALY
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1750
LONDON
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1773
LONDON
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WORKING WITHIN
THE LANGUAGE
OF CLASSICAL
ARCHITECTURE.
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“…[Architecture and Software patterns]
give us a vocabulary to talk about how
things are constructed. It is much more
convenient to say, ‘this object has listeners
for its properties,’ than ‘this object lets you
hook callback functions that are called
when properties change.’”
— Federico Mena Quintero
“Software that has the Quality Without a Name”
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Phi Beta Kappa Hall, Wren Building, William & Mary, Wiliamsburg, Virginia
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http://www.flickr.com/photos/cindy47452/3682879190/
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THE LANGUAGE WE USE
TO DESCRIBE OURSELVES
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craftSmen
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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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“
design patterns are
suggested approaches
seen in the wild.
- B R I A N H O G A N
”
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http://www.patterntap.com
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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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Charlottesville Downtown
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Shops at Stonefield
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“…the mere list of elements which are
typical in a given town tells us the
way of life of people there.”
— Alexander, TTWoB, pp71
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“To many software-patterns folk the quality
without a name doesn’t apply to things like
software anyhow. I agree that most software—
at least the software I see—doesn’t have such a
quality, but does that mean it couldn’t? I find it
odd, though, to take so much inspiration from
the simple, mechanical parts of a person’s work
—the form of the pattern language and terms
like forces—but to ignore the heart of it. I’m not
so sure the quality without a name is
irrelevant.”
— Richard P. Gabriel Patterns of Software, pp 71
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Objective
Quality
THIS IS AN
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Nature = 15 Properties in common
All patterns come from these properties
Each property can also transform
Only good design = transformation,
one property at a time.
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Thick Boundaries
Local Symmetries
Positive Space
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TRANSFORMATION
STRUCTURE-PRESERVING
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REFACTORING
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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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@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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2
COMPOSITION
DELEGATE
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FAT Models
D
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MODULES
CONCERNS
PLUGINS*
GEMS
ENGINES
2
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FAT Controllers
ONE CONTROLLER TO RULE THEM ALL... or not.
D
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TRANSACTIONALS
before_validation
before_validation on: :create
after_validation
after_validation on: :create
before_save
before_action
after_save
after_action
2
D
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http://callbackhell.com
D
fs.readdir(source, function (err, files) {
if (err) {
console.log('Error finding files: ' + err)
} else {
files.forEach(function (filename, fileIndex) {
console.log(filename)
gm(source + filename).size(function (err, values) {
if (err) {
console.log('Error identifying file size: ' + err)
} else {
console.log(filename + ' : ' + values)
aspect = (values.width / values.height)
widths.forEach(function (width, widthIndex) {
height = Math.round(width / aspect)
console.log('resizing ' + filename + 'to ' + height + 'x' + height)
this.resize(width, height).write(dest + 'w' + width + '_' + filename, function(err) {
if (err) console.log('Error writing file: ' + err)
})
}.bind(this))
}
})
})
}
})
CALLBACKS
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Keep Your Code Shallow
MODULARIZE (Make a library)
handle every single error
2
http://callbackhell.com
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“I USE
(DRUPAL|RAILS|FRAMEWORK.NAME)
TO BUILD EVERYTHING.”
D
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FRAMEWORKS ARE
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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M V C
2
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LOTS OF VIEW LOGIC
D
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2
TYPOGRAPHIC
REFACTORING
http://naildrivin5.com/blog/2013/05/17/source-code-typography.html
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def text_field_tag(name, value = nil, options = {})
tag :input, { :type => "text", :name => name, :id => sanitize_to_id(name), :value => value }.update(
end
def text_field_tag(name, value = nil, options = {})
tag :input,
{
:type => "text",
:name => name,
:id => sanitize_to_id(name),
:value => value
}.update(options.stringify_keys)
end
2
D
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Untested Code
D
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SAMPLE EXAMPLE
REFACTOR
TRACTOR
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PHONE CALL
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HALF
CALL
HALF
CALL
Gerard Meszaros “Pattern; Half Object + Protocol”
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HALF
CALL
HALF
CALL
Gerard Meszaros “Pattern; Half Object + Protocol”
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HALF
CALL
HALF
CALL
cALL
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HALF
CALL
HALF
CALL
HALF
CALL
cALL
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REFACTOR
NOT
THE GREAT REWRITE
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SO WHAT DO WE DO?
THE KERNEL
OF THE WAY
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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. ”
— Jeff 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 E N
”
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“...mediocre developers never even
ask why. They just arrive at the
first solution that works and keep
plowing ahead.”
— Jeff 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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“To many software-patterns folk the quality
without a name doesn’t apply to things like
software anyhow. I agree that most software—
at least the software I see—doesn’t have such a
quality, but does that mean it couldn’t? I find it
odd, though, to take so much inspiration from
the simple, mechanical parts of a person’s work
—the form of the pattern language and terms
like forces—but to ignore the heart of it. I’m not
so sure the quality without a name is
irrelevant.”
— Richard P. Gabriel Patterns of Software, pp 71
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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.”
— 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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REFACTORING
STRUCTURE-PRESERVING
TRANSFORMATIONS =
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LANGUAGE
LEARN TO
speak THE
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EVOLVES
SOFTWARE
THAT
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HAS NO NAME
THE
QUALITY
OF SOFTWARE
that
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The Three-book series
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@boboroshi
THANK YOU
[email protected]
https://speakerdeck.com/boboroshi
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