This document discusses refactoring code in Ruby. It provides examples of refactoring techniques like replacing conditionals with polymorphism, introducing named parameters, replacing magic numbers with symbolic constants, extracting surrounding methods, and replacing loops with closure methods. The goal of refactoring is to clean up code without changing its external behavior in order to make it more readable, flexible and maintainable.

1. Refatorando Código
Ruby
@caike
http://caikesouza.com
caike@envylabs.com

2. www.envylabs.com

3. Métodos
Ágeis

4. Testes

5. (Anti-)Patterns

6. Software
Craftsmanship

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

11. Refatorar é ...

12. Limpar a casa sem
mudar a fachada

14. Algumas razões

15. Design

16. Responder
a mudanças

17. Entregas
Constantes

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

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

20. Quando ?

21. novas features

22. bugs

24. Débito Técnico

25. Code Reviews

26. “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)

28. exemplos.rb

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

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

31. Replace Loop with
Closure Method

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

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

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

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

39. Introduce Explaining
Variable

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

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

43. Replace Temp
With Query

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

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

46. OMG OMG OMG OMG OMG

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

48. 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

49. Inline Method

50. 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

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

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

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

54. Replace Temp
With Chain

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

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

57. Command
vs.
Query

58. def expects
...
self
end
def with
...
self
end
def returns
...
self
end

59. 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

60. 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

61. Extract Surrounding
Method

62. def charge(amount, ccnumber)
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

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

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

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

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

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

68. Introduce Named Parameter

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

70. 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)

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

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

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

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

75. Replace Magic Number
with Symbolic Constant

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

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

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

79. 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

80. 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
if @type_code == :ultra_suspension
...
end
end

81. CLOSED for modification
OPEN for extension

83. Replace Conditional
With Polymorphism

84. class MountainBike
def price
...
end
end

85. module MountainBike
def price
...
end
end

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

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

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

89. 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

90. 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

91. 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

92. 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

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

95. Coding Dojo
http://orlandodojo.org/
http://dojorio.org/

97. 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