Refactoring

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

Orlando Ruby User GroupJanuary 2010

@caikehttp://caikesouza.com

Friday, January 15, 2010

http://caikesouza.com


Agile


Testing


Patterns


Professionalism


Software Craftsmanship


?Friday, January 15, 2010

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 worksWhen I refactor

Then it should be easier to understandAnd still work!


Cleaning up the house


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

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






wiki, Fit, JUnit

eXtreme Programming








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




Some reasons...


Design++


Money++


Money++Respond to changes


Money++Respond to changes

Release with confidence


Effort--


Jan Feb Mar Apr May Jun Jul

Cost of Maintenance

Waterfall

Extreme Programming Explained: Embrace ChangeAddison Wesley, 2000


Jan Feb Mar Apr May Jun Jul

Cost of Maintenance Extreme Programming Explained: Embrace ChangeAddison Wesley, 2000

XP


http://www.flickr.com/photos/x180/503574487/

code LESSsleep MORE




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


Code Smells

Duplicated Code


Long Method

Duplicated Code

Code Smells


Duplicated Code

Long Method

Large ClassCode Smells


Duplicated Code

Long Method

Divergent ChangeLarge ClassCode Smells


Duplicated Code

Long Method

Divergent ChangeLarge Class

Long ParameterList

Code Smells


Test Driven Development


RedGreen

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 withClosure Method


managers = []

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


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


class Movie def initialize(stars) @stars = stars end def recommended? ((@stars > 5) ? 8 : 1) >= 8 endend


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 ExplainingVariable


class Movie def initialize(stars) @stars = stars end def recommended? rating = (@stars > 5) ? 8 : 1 rating >= 8 endend


Replace TempWith Query


class Movie def initialize(stars) @stars = stars end def recommended? rating = (@stars > 5) ? 8 : 1 rating >= 8 endend


class Movie def initialize(stars) @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

endSaturday, January 16, 2010

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


Replace TempWith Chain


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


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


def expects ... selfend

def with ... selfend

def returns ... selfend


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 endend


Extract SurroundingMethod


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 endend


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


def connect begin conn = CC_Charger_Server.connect(...) yield conn rescue IOError => e Logger.log "Error: #{e}" return nil ensure conn.close endend


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, age, height, weight, metric_system) ...end


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


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


Replace Magic Number with Symbolic Constant


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


CONTACTS_PER_PAGE = 15

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


class MountainBike def price ... endend

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

endSaturday, January 16, 2010

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

if @type_code == :font_suspension (1 + @comission) * @base_price + @front_suspension_priceend if @type_code == :full_suspension (1 + @comission) * @base_price+

@front_suspension_price + @rear_suspension_price

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


Replace ConditionalWith Polymorphism


class MountainBike def price ... endend


module MountainBike def price ... endend


class RigidMountainBike include MountainBikeend

class FrontSuspensionMountainBike include MountainBikeend

class FullSuspensionMountainBike include MountainBikeend


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

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

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


class RigidMountainBike include MountainBike

def price (1 + @comission) * @base_price endend


def price if @type_code == :rigid raise "should not be called" 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


class FrontSuspensionMountainBike include MountainBike def price (1 + @comission) * @base_price + @front_suspension_price end end

class FullSuspensionMountainBike include MountainBike def price (1 + @comission) * @base_price + @front_suspension_price + @rear_suspension_price endend


def price if @type_code == :rigid raise "should not be called" end if @type_code == :font_suspension raise "should not be called" end if @type_code == :full_suspension raise "should not be called" end end


class RigidMountainBike include MountainBikeend

class FrontSuspensionMountainBike include MountainBikeend

class FullSuspensionMountainBike include MountainBikeend


Only the beginning...Saturday, January 16, 2010

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Coding Dojo

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Thank you!@caike





Refactoring

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