Refactoring

Refactoring
{ :from => :mess,
:to => :clean_code,
:through => :patterns }

@caike
Orlando Ruby User Group http://caikesouza.com
January 2010
Friday, January 15, 2010

Agile


Testing


Patterns


Professionalism


Software Craftsmanship


http://www.ﬂickr.com/photos/eurleif/255241547/


"Any fool can write code that
a computer can understand.
Good programmers write code that
humans can understand"
(Martin Fowler)


“Free software only matters
to those who can read”
(Robert M. Lefkowitz)


http://www.ﬂickr.com/photos/dhammza/91435718/


Given messy code that works
When I refactor
Then it should be easier to understand
And still work!


Cleaning up the house


http://www.ﬂickr.com/photos/benfrantzdale/208672143/

http://www.ﬂickr.com/photos/improveit/1574023621/


wiki, Fit, JUnit


eXtreme
Programming
http://www.ﬂickr.com/photos/improveit/1574023621/


http://www.ﬂickr.com/photos/adewale_oshineye/2933030620


Some reasons...


Design++


Money++


Respond to changes
Money++


Respond to changes
Money++
Release with conﬁdence


Effort--


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


code LESS
sleep MORE
http://www.ﬂickr.com/photos/x180/503574487/


http://www.ﬂickr.com/photos/rockinrob/1485573200/


When ?


When you add a function


When you ﬁx a bug


Code Reviews


http://www.ﬂickr.com/photos/highwayoﬂife/2699887178/


Code Smells


Duplicated Code

Code Smells


Duplicated Code

Code Smells
Long Method


Duplicated Code
Large Class
Code Smells
Long Method


Duplicated Code
Large Class Divergent Change
Code Smells
Long Method


Duplicated Code
Large Class Divergent Change
Code Smells
Long Parameter
List Long Method


Test Driven
Development


Red
Green
Refactor


What if I Don’t ?


Debt Metaphor


http://www.ﬂickr.com/photos/didmyself/3050138294/


Get ready for code!


managers = []

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

Saturday, January 16, 2010

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


http://www.ﬂickr.com/photos/anirudhkoul/3804552280/


http://www.bartcop.com/marilyn-monroe001.jpg


http://thetorchonline.com/wp-content/uploads/2009/04/deathstar.jpg


Introduce Explaining
Variable


class Movie
@stars = stars
end

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


Replace Temp
With Query


class Movie
@stars = stars
end

def recommended?
rating >= 8
end

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

OMG,
This is sooooo cooooool!


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

Inline Method


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([])


Replace Temp
With Chain


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


def expects
...
self
end

def with
...
self
end

def returns
...
self
end


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


Extract Surrounding
Method


def charge(amount, ccnumber)
connect do |conn|
conn.send(amount, ccnumber)
end
end


def connect
begin
conn = CC_Charger_Server.connect(...)
yield conn
rescue IOError => e
Logger.log "Error: #{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)


Introduce Named Parameter


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


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)


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

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


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


class FrontSuspensionMountainBike
def price
end
end

class FullSuspensionMountainBike
def price
end
end


def price
end
end
end
end


Only the beginning...

Coding Dojo

http://www.ﬂickr.com/photos/el_ser_lomo/3267627038/

http://orlandodojo.wordpress.com/
http://groups.google.com/group/orlando-dojo/

Thank you!
@caike
http://caikesouza.com


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