Refactoring Ruby Code

Refatorando Código
Ruby

@caike
http://caikesouza.com
caike@envylabs.com

"Any fool can write code that
a computer can understand.
Good programmers write code that
humans can understand"

(Martin Fowler)

Limpar a casa sem
mudar a fachada

Waterfall

Jan Feb Mar Apr May Jun Jul

Cost of Maintenance Extreme Programming Explained: Embrace Change
Addison Wesley, 2000

XP

Jan Feb Mar Apr May Jun Jul

Cost of Maintenance Extreme Programming Explained: Embrace Change
Addison Wesley, 2000

“The great thing about programming is
pretty much everyone's code is shit.
Writing software is hard, so it's no problem
ﬁnding dogs in someone's stuff”

(Zed Shaw)

managers = []

employees.each do |e|
managers << e if e.is_manager?
end

Replace Loop with
Closure Method

managers = employees.
select { |e| e.is_manager? }

class Movie
def initialize(stars)
@stars = stars
end

def recommended?
((@stars > 5) ? 8 : 1) >= 8
end
end

Introduce Explaining
Variable

class Movie
@stars = stars
end

def recommended?
rating = (@stars > 5) ? 8 : 1
rating >= 8
end
end

class Movie
@stars = stars
end

def recommended?
rating >= 8
end

def rating
(@stars > 5) ? 8 : 1
end
end

class Movie

def recommended?
rating >= 8
end

def rating
(@stars > 5) ? 8 : 1
end
end

class Movie

def recommended?
rating >= 8
end

def rating
more_than_five_stars? ? 8 : 1
end

def more_than_five_stars?
@stars > 5
end
end

class Movie
def initialize...end
def recommended?
rating >= 8
end

def rating
more_than_five_stars? ? 8 : 1
end

def more_than_five_stars?
@stars > 5
end
end

class Movie
def initialize...end
def recommended?
rating >= 8
end

def rating
@stars > 5 ? 8 : 1
end

end

mock = mock('user')
expectation = mock.expects(:find)
expectation.with("1")
expectation.returns([])

mock = mock('user')
mock.expects(:find).with("1").
returns([])

def expects
...
self
end

def with
...
self
end

def returns
...
self
end

def charge(amount, card_number)
begin
conn = CC_Charger_Server.connect(...)
conn.send(amount, card_number)
rescue IOError => e
Logger.log "Error: #{e}"
return nil
ensure
conn.close
end
end

Extract Surrounding
Method

def charge(amount, ccnumber)
begin
rescue IOError => e
return nil
ensure
conn.close
end
end

def charge(amount, card_number)
connect do |conn|
end
end

def connect
begin
yield conn
rescue IOError => e
return nil
ensure
conn.close
end
end

def body_fat_percentage(name,
age, height, weight, metric_system)
...
end

body_fat_percentage("fred", 30, 1.82, 90, 1)
body_fat_percentage("joe", 32, 6, 220, 2)

body_fat_percentage("fred", :age => 30,
:height => 1.82, :weight => 90,
MetricSystem::METERS_KG)

body_fat_percentage("joe", :age => 32,
:height => 6, :weight => 220,
MetricSystem::FEET_LB)

def body_fat_percentage(name, params={})
# params[:age]
# params[:height]
# params[:weight]
# params[:metric_system]
end

user.posts.paginate(:page => params[:page],
:per_page => params[:per_page] || 15)

Replace Magic Number
with Symbolic Constant

CONTACTS_PER_PAGE = 15

user.posts.paginate(:page => params[:page],
:per_page => params[:per_page] ||
CONTACTS_PER_PAGE)

class MountainBike
def price
...
end
end

MountainBike.new(:type => :rigid, ...)
MountainBike.new(:type => :front_suspension, ...)
MountainBike.new(:type => :full_suspension, ...)

def price
if @type_code == :rigid
(1 + @comission) * @base_price
end
if @type_code == :font_suspension
(1 + @comission) * @base_price +
@front_suspension_price
end
if @type_code == :full_suspension
(1 + @comission) * @base_price+
@front_suspension_price +
@rear_suspension_price
end

end

def price
end
end
end
if @type_code == :ultra_suspension
...
end
end

CLOSED for modiﬁcation
OPEN for extension

Replace Conditional
With Polymorphism

class MountainBike
def price
...
end
end

module MountainBike
def price
...
end
end

class RigidMountainBike
include MountainBike
end

class FrontSuspensionMountainBike
end

class FullSuspensionMountainBike
end

RigidMountainBike.new(:type => :rigid, ...)

FrontSuspensionMountainBike.new(:type =>
:front_suspension, ...)

FullSuspensionMountainBike.new(:type =>
:full_suspension, ...)

class RigidMountainBike

def price
end
end

class FrontSuspensionMountainBike
def price
end
end

class FullSuspensionMountainBike
def price
end
end

def price
raise "should not be called"
end
end
end
end

def price
end
end
end
end

Coding Dojo

http://orlandodojo.org/
http://dojorio.org/

Obrigado!
http://www.flickr.com/photos/eurleif/255241547/
http://www.flickr.com/photos/dhammza/91435718/
http://www.flickr.com/photos/krash0387
http://www.flickr.com/photos/benfrantzdale/208672143/
http://www.flickr.com/photos/improveit/1574023621/
http://www.flickr.com/photos/aaroncoyle/972403508
http://www.flickr.com/photos/talios/3726484920
http://www.flickr.com/photos/moow/3412079622
http://www.flickr.com/photos/highwayoflife/2699887178/

@caike
http://caikesouza.com
http://smallactsmanifesto.org

Refactoring Ruby Code

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