The document discusses various techniques for refactoring Ruby code including improving readability, maintainability, and extensibility while preserving existing behavior. It provides examples of simplifying conditional logic, reducing duplication, improving brevity, and leveraging built-in Ruby methods and syntax.

1. Refactor Like A Boss
a few techniques for everyday Ruby hacking

2. Refactoring
The process of changing code
without modifying behavior

3. Ungoals of refactoring
• Brevity for the sake of brevity
• To demonstrate mastery of Ruby or design patterns

4. Goals of refactoring
• Improve readability
• Improve maintainability
• Improve extensibility
• Promote an expressive API
• Reduce complexity

5. Ruby freebies

6. DRY Assignment
if 1 > 0
@foo = 'bar'
else
@foo = 'baz'
end
@foo # => 'bar'

7. DRY Assignment
@foo = if 1 > 0
'bar'
else
'baz'
end
@foo # => 'bar'

8. DRY Assignment
@foo = case 1
when 0..1
'bar'
else
'baz'
end
@foo # => 'bar'

9. Ternary operator
@foo = 1 > 0 ? 'bar' : 'qux'
@foo # => 'bar'

10. Ternary operator
def postive?(number)
number > 0 ? 'yes' : 'no'
end
positive?(100) # => 'yes'

11. Bang bang
def foo?
if @foo
true
else
false
end
end

12. Bang bang
def foo?
@foo ? true : false
end

13. Bang bang
def foo?
!!@foo
end

14. Conditional assignment
if not @foo
@foo = 'bar'
end

15. Conditional assignment
unless @foo
@foo = 'bar'
end

16. Conditional assignment
@foo = 'bar' unless @foo

17. Conditional assignment
@foo ||= 'bar'

18. Parallel assignment
@foo = 'baz'
@bar = 'qux'
# => "baz"
# => "qux"

19. Parallel assignment
@foo, @bar = 'baz', 'qux'
# => ["baz", "qux"]
@foo # => "baz"

20. Multiple return
def get_with_benchmark(uri)
res = nil
bench = Benchmark.measure do
res = Net::HTTP.get_response(uri)
end
return res, bench.real
end
@response, @benchmark = get_with_benchmark(@uri)
# => [#<Net::HTTPOK 200 OK>, 0.123]

21. Implied begin
def my_safe_method
begin
do_something_dangerous()
true
rescue
false
end
end

22. Implied begin
def my_safe_method
do_something_dangerous()
true
rescue
false
end

23. Exception lists
def self.likelihood_of_rain
Hpricot::XML(weather_xml)/'probability-of-rain'
rescue Net::HTTPBadResponse,
Net::HTTPHeaderSyntaxError,
Net::ProtocolError
return false
end
def self.likelihood_of_snow
Hpricot::XML(weather_xml)/'probability-of-snow'
rescue Net::HTTPBadResponse,
Net::HTTPHeaderSyntaxError,
Net::ProtocolError
return false
end

24. Exception lists
NET_EXCEPTIONS = [ Net::HTTPBadResponse,
Net::HTTPHeaderSyntaxError,
Net::ProtocolError ]
def self.likelihood_of_rain
Hpricot::XML(weather_xml)/'probability-of-rain'
rescue NET_EXCEPTIONS
return false
end
def self.likelihood_of_snow
Hpricot::XML(weather_xml)/'probability-of-snow'
rescue NET_EXCEPTIONS
return false
end

25. Symbol to Proc
(1..5).map{|number| number.to_s }
# => ["1", "2", "3", "4", "5"]

26. Symbol to Proc
(1..5).map(&:to_s)
# => ["1", "2", "3", "4", "5"]

27. MapReduce
def fibonacci_sum
sum = 0
[1,1,2,3,5,8,13].each{|int| sum += int }
sum
end
fibonacci_sum() # => 33

28. MapReduce
def fibonacci_sum
[1,1,2,3,5,8,13].reduce(0){|sum, int| sum + int }
end
fibonacci_sum() # => 33

29. MapReduce
{:foo => 'bar'}.inject({}) do |memo, (key, value)|
memo[value] = key
memo
end
# => {"bar" => :foo}

30. Regex captures
match_data = 'my lil string'.match(/my (w+) (w+)/)
match_data.captures[0] # => "lil"
match_data.captures[1] # => "string"
match_data.captures[2] # => nil

31. Regex captures
'my lil string'.match(/my (w+) (w+)/)
$1 # => "lil"
$2 # => "string"
$3 # => nil

32. Regex captures
'my lil string' =~ /my (w+) (w+)/
$1 # => "lil"
$2 # => "string"
$3 # => nil

33. tap
def Resource.create
resource = Resource.new
resource.save
resource
end
# => #<Resource:0xffffff>

34. tap
def Resource.create
Resource.new.tap{|resource| resource.save }
end
# => #<Resource:0xffffff>

35. sprintf
sprintf("%d as hexadecimal: %04x", 123, 123)
# => "123 as hexadecimal: 007b"
"%d as hexadecimal: %04x" % [123, 123]
# => "123 as hexadecimal: 007b"
"%s string" % ['my']
# => "my string"

36. case equality
def cerealize(val)
if val.is_a?(Numeric) || val.is_a?(String)
val
elsif val.is_a?(Enumerable)
val.to_json
else
val.to_s
end
end

37. case equality
def cerealize(val)
case val
when Numeric, String
val
when Enumerable
val.to_json
else
val.to_s
end
end

38. case equality
if command =~ /sudo/
raise 'Danger!'
elsif command =~ /^rm /
puts 'Are you sure?'
else
puts 'Run it.'
end

39. case equality
case command
when /sudo/
raise 'Danger!'
when /^rm /
puts 'Are you sure?'
else
puts 'Run it.'
end

40. Splat Array
def shopping_list(ingredients)
unless ingredients.is_a?(Array)
ingredients = [ingredients]
end
ingredients.join(", ")
end
shopping_list("eggs")
# => "eggs"
shopping_list(["eggs", "bacon"])
# => "eggs, bacon"

41. Splat Array
def shopping_list(ingredients)
[ingredients].flatten.join(", ")
end
shopping_list("eggs")
# => "eggs"
shopping_list(["eggs", "bacon"])
# => "eggs, bacon"

42. Splat Array
def shopping_list(ingredients)
[*ingredients].join(", ")
end
shopping_list("eggs")
# => "eggs"
shopping_list(["eggs", "bacon"])
# => "eggs, bacon"

43. Splat args
def shopping_list(*ingredients)
ingredients.join(", ")
end
shopping_list("eggs")
# => "eggs"
shopping_list(["eggs", "bacon"])
# => "eggs, bacon"
shopping_list("eggs", "bacon")
# => "eggs, bacon"

44. Rails freebies

45. blank?
if @user.name and !@user.name.empty?
puts @user.name
else
puts "no name"
end

46. blank?
if @user.name.blank?
puts "no name"
else
puts @user.name
end

47. present?
if @user.name.present?
puts @user.name
else
puts "no name"
end

48. presence
puts @user.name.presence || "no name"

49. truncate
opening = "A long time ago in a galaxy far, far away"
if opening.size > 20
opening[0..16] + "..."
end
# => "A long time ago i..."

50. truncate
opening = "A long time ago in a galaxy far, far away"
opening.truncate(20)
# => "A long time ago i..."

51. truncate
opening = "A long time ago in a galaxy far, far away"
opening.truncate(20, :separator => ' ')
# => "A long time ago..."

52. try
@existing = User.find_by_email(@new.email)
@existing.destroy if @existing

53. try
User.find_by_email(@new.email).try(:destroy)

54. in?
if admin_roles.include? @user.role
puts "Hi Admin!"
end

55. in?
if @user.role.in? admin_roles
puts "Hi Admin!"
end

56. Delegation
class User
has_one :account
def balance
self.account.balance
end
def balance=(amount)
self.account.balance=(amount)
end
end

57. Delegation
class User
has_one :account
delegate :balance, :balance=, :to => :account
end

58. Memoization
class Avatar
def file_size
if @file_size
return @file_size
else
result = some_expensive_calculation
result += more_expensive_calculation
@file_size = result
end
end
end

59. Memoization
class Avatar
extend ActiveSupport::Memoizable
def file_size
result = some_expensive_calculation
result += more_expensive_calculation
end
memoize :file_size
end

60. alias_method_chain
alias_method :translate_without_log, :translate
def translate_with_log(*args)
result = translate_without_log(*args)
Rails.logger.info result
result
end
alias_method :translate, :translate_with_log

61. alias_method_chain
def translate_with_log(*args)
result = translate_without_log(*args)
Rails.logger.info result
result
end
alias_method_chain :translate, :log

62. class_attribute
class Resource
class < self
def host=(name)
@host = hame
end
def host
@host
end
end
end

63. class_attribute
class Resource
class < self
attr_accessor :host
end
end

64. class_attribute
class Resource
class_attribute :host
end

65. Hash#symbolize_keys
my_hash = { 'foo' => 123 }.symbolize_keys
my_hash['foo']
# => nil
my_hash[:foo]
# => 123

66. Hash#stringify_keys
my_hash = { :foo => 123 }.stringify_keys
my_hash['foo']
# => 123
my_hash[:foo]
# => nil

67. HashWithIndifferentAccess
my_hash = { :foo => 123 }
my_hash['foo']
# => nil
my_hash[:foo]
# => 123

68. HashWithIndifferentAccess
my_hash = { :foo => 123 }.with_indifferent_access
my_hash['foo']
# => 123
my_hash[:foo]
# => 123

69. forty_two
my_array = []
my_array[41] = "the answer"
my_array[41]
# => "the answer"

70. forty_two
my_array = []
my_array[41] = "the answer"
my_array.forty_two
# => "the answer"

71. slideshare gsterndale
github gsterndale
irc sternicus