This document discusses refactoring code to improve its structure and design without changing its external behavior. It provides examples of refactoring techniques like extracting methods, replacing conditionals with polymorphism, introducing named parameters, and replacing magic numbers with symbolic constants. The goal of refactoring is to make code easier to understand and cheaper to modify over time.

1. Refactoring
.... porque apenas fazer
funcionar não é o suficiente.
@caike
caikesouza.com

2. www.envylabs.com

3. Orlando Coding Dojo
http://orlandodojo.org

4. Refatorar é...
realizar mudanças internas em um
programa funcional com o objetivo torná-lo
mais fácil de ser compreendido e mais
barato de ser modificado - sem que haja
mudanças no comportamento externo;

5. Limpar a casa sem
mudar a fachada

6. Métodos
Ágeis

8. eXtreme
Programming

9. Scrum ?

10. Testes

11. (Anti-)Patterns

12. Software
Craftsmanship

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

16. Benefícios

17. Design

18. Responder
a mudanças

19. Entregas
Constantes

20. Waterfall
Jan Feb Mar Apr May Jun Jul
Cost of Maintenance Extreme Programming Explained: Embrace Change
Addison Wesley, 2000

21. XP
Jan Feb Mar Apr May Jun Jul
Cost of Maintenance Extreme Programming Explained: Embrace Change
Addison Wesley, 2000

22. Quando ?

23. novas features

24. TDD

25. Red
Green
Refactor

26. bugs

27. TDD

28. Red
Green
Refactor

29. Code Reviews

30. om
c o
e çã
il izReviews
Code ra
t e
U d
m o

31. “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)

33. Débito Técnico

34. exemplos.rb

35. managers = []
employees.each do |e|
managers << e if e.is_manager?
end

36. managers = []
employees.each do |e|
managers << e if e.is_manager?
end

37. Replace Loop with
Closure Method

38. managers = []
employees.each do |e|
managers << e if e.is_manager?
end

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

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

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

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

46. Introduce Explaining
Variable

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

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

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

50. Replace Temp
With Query

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

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

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

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

55. OMG OMG OMG OMG OMG

56. 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

57. 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

58. Inline Method

59. 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

60. class Movie
def initialize...end
def recommended?
rating >= 8
end
def rating
@stars > 5 ? 8 : 1
end
end

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

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

63. Replace Magic Number
with Symbolic Constant

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

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

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

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

68. Replace Temp
With Chain

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

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

71. Command
vs.
Query

72. def expects
...
self
end
def with
...
self
end
def returns
...
self
end

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

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

75. Extract Surrounding
Method

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

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

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

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

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

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

82. Introduce Named Parameter

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

84. 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)

85. 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 })

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

87. class MountainBike
def price
...
end
end
MountainBike.new(:type => :rigid, ...)
MountainBike.new(:type => :front_suspension, ...)
MountainBike.new(:type => :full_suspension, ...)

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

89. def price
if @type == :rigid
(1 + @comission) * @base_price
end
if @type == :font_suspension
(1 + @comission) * @base_price +
@front_suspension_price
end
if @type == :full_suspension
(1 + @comission) * @base_price+
@front_suspension_price +
@rear_suspension_price
end
if @type == :ultra_suspension
...
end
end

90. FECHADAS
para modificações
ABERTAS
para extensões

92. Replace Conditional
With Polymorphism

93. class MountainBike
def price
...
end
end

94. module MountainBike
def price
...
end
end

95. class RigidMountainBike
include MountainBike
end
class FrontSuspensionMountainBike
include MountainBike
end
class FullSuspensionMountainBike
include MountainBike
end

96. RigidMountainBike.new(:type => :rigid, ...)
FrontSuspensionMountainBike.new(:type =>
:front_suspension, ...)
FullSuspensionMountainBike.new(:type =>
:full_suspension, ...)

97. class RigidMountainBike
include MountainBike
def price
(1 + @comission) * @base_price
end
end

98. def price
if @type == :rigid
raise "should not be called"
end
if @type == :font_suspension
(1 + @comission) * @base_price +
@front_suspension_price
end
if @type == :full_suspension
(1 + @comission) * @base_price+
@front_suspension_price +
@rear_suspension_price
end
end

99. 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
end
end

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

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

102. class RigidMountainBike
include MountainBike
end
class FrontSuspensionMountainBike
include MountainBike
end
class FullSuspensionMountainBike
include MountainBike
end

103. Já posso ser um
Programador
RockStar ?

104. NÃO

105. “I’m not a great programmer.
I’m just a good programmer
with great habits”
(Kent Beck)

106. "People are non-linear,
first-order components in
software development"
(Alistair Cockburn)

108. Refactoring
.... porque apenas fazer
funcionar não é o suficiente.
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/ @caike
http://www.flickr.com/photos/aaroncoyle/972403508
http://www.flickr.com/photos/talios/3726484920
http://www.flickr.com/photos/moow/3412079622
caikesouza.com
http://www.flickr.com/photos/highwayoflife/2699887178/