Coding Confidently With Ruby

A talk for Ruby Conf PH 2015

Transcript

1. CODING DENTLY CONFI WITH RUBY Maricris Nonato @maricris_sn 27.03.2015
2. bit.ly/msn-ccwruby
3. premierespeakers.com
4. http://philippineslifestyle.com/wp-content/uploads/pet-2.jpg
5. http://blog.jelastic.com/wp-content/uploads/2012/11/super_duper_awesome_programmer_thumb.png
6. https://s-media-cache-ak0.pinimg.com/736x/7e/e8/d0/7ee8d085d9ba030b5a0011fe7105dae6.jpg
7. http://www.ecyc.org/sites/default/files/storytelling-circle-cropped.jpg
8. DATA INPUTS RETURNING DATA EXCEPTIONS/ERROR HANDLING
9. “If we have data, let’s look at data. If all we have are opinions, let’s go with mine” Jim Barksdale, former Netscape CEO
10. https://s-media-cache-ak0.pinimg.com/236x/29/b7/9c/29b79cc99043421f5dd8ebeda5481623.jpg
11. Your friendly neighbor: Ruby’s conversion methods DATA INPUTS
12. Method Target Class Type Notes #to_a Array Explicit #to_ary Array Implicit #to_c Complex Explicit #to_h Hash Explicit Introduced in Ruby 2.0 #to_i Integer Explicit #to_int Integer Implicit #to_path String Implicit #to_r Rational Explicit #to_regexp Regexp Implicit Used by Regexp.try_convert #to_s String Explicit #to_str String Implicit #to_sym Symbol Implicit
13. Implicit vs Explicit DATA INPUTS
14. DATA INPUTS
15. class Cat def initialize(breed, color) @breed = breed @color = color end end cat = Cat.new(breed: 'Munchkin cat', color: 'ginger') DATA INPUTS
16. class Cat def initialize(breed, color) @breed = breed @color = color end end cat = Cat.new(breed: 'Munchkin cat', color: 'ginger') DATA INPUTS puts "I'm looking for a " + cat # => TypeError: can't convert Cat into String # Implicit
17. class Cat def initialize(breed, color) @breed = breed @color = color end end cat = Cat.new(breed: 'Munchkin cat', color: 'ginger') DATA INPUTS puts "I'm looking for a “ + cat.to_s # => I have a #<Cat:0x007f81a40ce1d0> # Explicit puts "I'm looking for a " + cat # => TypeError: can't convert Cat into String # Implicit
18. class Cat def initialize(breed, color) @breed = breed @color = color end end cat = Cat.new(breed: 'Munchkin cat', color: 'ginger') DATA INPUTS puts "I'm looking for a “ + cat.to_s # => I have a #<Cat:0x007f81a40ce1d0> # Explicit puts "I'm looking for a " + cat # => TypeError: can't convert Cat into String # Implicit # String Interpolation puts "I'm looking for a #{cat}” # => I have a #<Cat:0x007f81a40ce1d0>
19. Sounds like a duck? Must be a duck! DATA INPUTS
20. DATA INPUTS
21. class Duck def quack 'Quack!' end end DATA INPUTS
22. class Duck def quack 'Quack!' end end DATA INPUTS class DuckRecording def quack play end def play 'Quack!' end end
23. class Duck def quack 'Quack!' end end DATA INPUTS class DuckRecording def quack play end def play 'Quack!' end end def make_it_quack(duck) duck.quack end # => “Quack!” puts make_it_quack(Duck.new) # => “Quack!” puts make_it_quack(DuckRecording.new)
24. Duck typing & Respond_to? DATA INPUTS
25. DATA INPUTS
26. class Duck def quack 'Quack!' end end DATA INPUTS
27. class Duck def quack 'Quack!' end end class Cow def moo 'Moooo' end end DATA INPUTS
28. class Duck def quack 'Quack!' end end class Cow def moo 'Moooo' end end class DuckRecording def quack play end def play 'Quack!' end end DATA INPUTS
29. class Duck def quack 'Quack!' end end class Cow def moo 'Moooo' end end class DuckRecording def quack play end def play 'Quack!' end end DATA INPUTS def make_it_quack(animal) animal.moo if animal.is_a?(Cow) end def make_it_quack(animal) raise TypeError unless animal.is_a?(Duck) end
30. class Duck def quack 'Quack!' end end class Cow def moo 'Moooo' end end class DuckRecording def quack play end def play 'Quack!' end end DATA INPUTS def make_it_quack(animal) animal.moo if animal.is_a?(Cow) end def make_it_quack(animal) raise TypeError unless animal.is_a?(Duck) end
31. DATA INPUTS
32. DATA INPUTS def make_it_quack(animal) animal.quack if animal.respond_to?(quack) end #Solution #1:
33. DATA INPUTS def make_it_quack(animal) animal.quack if animal.respond_to?(quack) end #Solution #1: def make_it_quack(animal) animal.soundoff end #Solution #2:
34. class Cow def soundoff moo end end class Duck def soundoff quack end end DATA INPUTS def make_it_quack(animal) animal.quack if animal.respond_to?(quack) end #Solution #1: def make_it_quack(animal) animal.soundoff end #Solution #2:
35. Don’t act like it.. Be it! DATA INPUTS
36. DATA INPUTS
37. Rational() DATA INPUTS
38. Rational() Array() DATA INPUTS
39. Rational() Array() String() DATA INPUTS
40. Rational() Array() String() Integer() DATA INPUTS
41. Rational() Array() Float() String() Integer() DATA INPUTS
42. Rational() Array() Float() String() Complex() Integer() DATA INPUTS
43. Rational() Array() Float() String() Complex() Integer() Hash() DATA INPUTS
44. Conversion using Ruby’s conversion functions DATA INPUTS
45. DATA INPUTS
46. Integer(10) # => 10 Integer(10.1) # => 10 Integer(“0x10") # => 16 Integer(0x10) # => 16 Integer(“010") # => 8 Integer(“0b10") # => 2 Integer(Time.now) # => 1427065879 Integer("cats”) # ArgumentError DATA INPUTS
47. Integer(10) # => 10 Integer(10.1) # => 10 Integer(“0x10") # => 16 Integer(0x10) # => 16 Integer(“010") # => 8 Integer(“0b10") # => 2 Integer(Time.now) # => 1427065879 Integer("cats”) # ArgumentError DATA INPUTS (10).to_int # => 10 (10.1).to_int # => 10 (“0x10”).to_int # NoMethodError (0x10).to_int # => 16 (“010”).to_int # NoMethodError (“0b10”).to_int # NoMethodError (Time.now).to_int # NoMethodError (“cats”).to_int # NoMethodError
48. Integer(10) # => 10 Integer(10.1) # => 10 Integer(“0x10") # => 16 Integer(0x10) # => 16 Integer(“010") # => 8 Integer(“0b10") # => 2 Integer(Time.now) # => 1427065879 Integer("cats”) # ArgumentError DATA INPUTS (10).to_int # => 10 (10.1).to_int # => 10 (“0x10”).to_int # NoMethodError (0x10).to_int # => 16 (“010”).to_int # NoMethodError (“0b10”).to_int # NoMethodError (Time.now).to_int # NoMethodError (“cats”).to_int # NoMethodError (10).to_i # => 10 (10.1).to_i # => 10 (“0x10”).to_i # => 0 (0x10).to_i # => 16 (“010”).to_i # => 10 (“0b10”).to_i # => 0 (Time.now).to_i # 1427065879 (“cats”).to_i # => 0
49. It’s not enough? Then make your own DATA INPUTS
50. DATA INPUTS Conversion method for convenience
51. def point_label(point) point.to_latlng if point.respond_to?(:to_latlng) end DATA INPUTS Conversion method for convenience
52. def point_label(point) point.to_latlng if point.respond_to?(:to_latlng) end DATA INPUTS class MapPoint def initialize(x, y) @x, @y = x, y end def to_latlng “location at: #{@x}, #{@y}” end end Conversion method for convenience
53. def point_label(point) point.to_latlng if point.respond_to?(:to_latlng) end DATA INPUTS class MapPoint def initialize(x, y) @x, @y = x, y end def to_latlng “location at: #{@x}, #{@y}” end end Conversion method for convenience point_label(MapPoint.new(11.9694, 121.9272)) # => ”location at: 11.9694, 121.9272"
54. def money_on_wallet(peso, bitcoin) peso + bitcoin end DATA INPUTS Conversion function for strict requirements
55. def money_on_wallet(peso, bitcoin) peso + bitcoin end DATA INPUTS Conversion function for strict requirements def money_on_wallet(peso, bitcoin) peso.to_f + (bitcoin.to_f * 1.5) end def money_on_wallet(peso, bitcoin) Float(peso) + (Float(bitcoin) * 1.5) end
56. DATA INPUTS Conversion function for strict requirements
57. def money_on_wallet(peso, bitcoin) Peso(peso) + bitcoin.to_peso end DATA INPUTS Conversion function for strict requirements
58. def money_on_wallet(peso, bitcoin) Peso(peso) + bitcoin.to_peso end DATA INPUTS Conversion function for strict requirements class Bitcoin def initialize(value) @value = value end def to_peso Peso(@value) * 1.5 end end def Peso(input) raise TypeError if input.is_a?(String) Float(input) end
59. If it can fail, it will fail! So, fail early! DATA INPUTS
60. DATA INPUTS
61. DATA INPUTS class Person def initialize(name, birthdate) @name = name @birthdate = birthdate end end
62. def age if birthdate.present? # do something else 0 end end DATA INPUTS class Person def initialize(name, birthdate) @name = name @birthdate = birthdate end end
63. def minor? begin if birthdate + 18.years < Date.today # do something end rescue # error when birthdate is nil end end def age if birthdate.present? # do something else 0 end end DATA INPUTS class Person def initialize(name, birthdate) @name = name @birthdate = birthdate end end
64. def minor? begin if birthdate + 18.years < Date.today # do something end rescue # error when birthdate is nil end end def age if birthdate.present? # do something else 0 end end DATA INPUTS class Person def initialize(name, birthdate) @name = name @birthdate = birthdate end end
65. DATA INPUTS
66. require 'date' class Person def initialize(name, birthdate) @name = name self.birthdate = birthdate end def birthdate=(new_birthdate) raise TypeError, "Invalid birth date" unless new_birthdate.is_a?(Date) @birthdate = new_birthdate end end DATA INPUTS
67. DATA INPUTS person = Person.new(“Marilyn”, “01/01/1958”) TypeError: Invalid birth date from (irb):114:in `birthdate=' from (irb):110:in `initialize' from (irb):134:in `new' from (irb):134 from /bin/irb:11:in `<main>' person = Person.new(“Enzo”, Date.new(2011,03,26)) => #<Person:0x007f980901b190 @name="Enzo", @birthdate=#<Date: 2011-03-26 ((2455647j,0s,0n), +0s,2299161j)>>
68. require 'date' class Person def initialize(name, birthdate) @name = name self.birthdate = birthdate end def birthdate=(new_birthdate) raise TypeError, "Invalid birth date" unless new_birthdate.is_a? (Date) @birthdate = new_birthdate end def age now = Date.today now.year - @birthdate.year - ((now.month > @birthdate.month || (now.month == @birthdate.month && now.day >= @birthdate.day)) ? 0 : 1) end def minor? true if age < 18 end end DATA INPUTS
69. The power of fetch DATA INPUTS
70. DATA INPUTS
71. h = { foo: false, bar: nil } DATA INPUTS
72. h = { foo: false, bar: nil } DATA INPUTS # test for key 'foobar' h.has_key?(:foobar) && h[:foobar].present?
73. h = { foo: false, bar: nil } DATA INPUTS # test for key 'foobar' h.has_key?(:foobar) && h[:foobar].present? # ambiguity demonstrated
74. h = { foo: false, bar: nil } DATA INPUTS # test for key 'foobar' h.has_key?(:foobar) && h[:foobar].present? # ambiguity demonstrated h[:foobar].inspect # => “nil” h[:foo].inspect # => “false” h[:bar].inspect # => “nil” h.fetch(:foobar) # => "KeyError: key not found: :foobar" h.fetch(:foo) # => false h.fetch(:bar) # => nil
75. h = { foo: false, bar: nil } DATA INPUTS # test for key 'foobar' h.has_key?(:foobar) && h[:foobar].present? # ambiguity demonstrated h[:foobar].inspect # => “nil” h[:foo].inspect # => “false” h[:bar].inspect # => “nil” h.fetch(:foobar) # => "KeyError: key not found: :foobar" h.fetch(:foo) # => false h.fetch(:bar) # => nil # error can be customised as well! raise KeyError, "Ooops, that key is missing!”
76. DATA INPUTS • fetch(key_name): get the value if the key exists, raise a KeyError if it doesn’t • fetch(key_name, default_value): get the value if the key exists, return default_value otherwise • fetch(key_name) { |key| "default" }: get the value if the key exists, otherwise run the supplied block and return the value.
77. DATA INPUTS
78. DATA INPUTS h = { foo: false, bar: nil }
79. DATA INPUTS h = { foo: false, bar: nil } h.fetch(:foobar) KeyError: key not found: :foobar from (irb):159:in `fetch' from (irb):159 from /bin/irb:11:in `<main>'
80. DATA INPUTS h = { foo: false, bar: nil } h.fetch(:foobar, “Hello world!” => "Hello World!" h.fetch(:foobar) KeyError: key not found: :foobar from (irb):159:in `fetch' from (irb):159 from /bin/irb:11:in `<main>'
81. DATA INPUTS h = { foo: false, bar: nil } h.fetch(:foobar, “Hello world!” => "Hello World!" h.fetch(:foobar) { |key| “Hello again World!” } => "Hello again World!" h.fetch(:foobar) KeyError: key not found: :foobar from (irb):159:in `fetch' from (irb):159 from /bin/irb:11:in `<main>'
82. Special cases as objects DATA INPUTS
83. def current_user if session[:user_id] User.find(session[:user_id]) end end def greeting "Hello, " + current_user.name : "Anonymous" end if current_user render_logout_button else render_login_button end DATA INPUTS
84. DATA INPUTS
85. class GuestUser def initialize(session) @session = session end def name "Anonymous" end def authenticated? false end end DATA INPUTS
86. class GuestUser def initialize(session) @session = session end def name "Anonymous" end def authenticated? false end end def current_user if session[:user_id] User.find(session[:user_id]) else GuestUser.new(session) end end DATA INPUTS
87. class GuestUser def initialize(session) @session = session end def name "Anonymous" end def authenticated? false end end def current_user if session[:user_id] User.find(session[:user_id]) else GuestUser.new(session) end end DATA INPUTS def greeting "Hello, #{current_user.name}" end if current_user.authenticated? render_logout_button else render_login_button end
88. When you’re benign, you’re fine DATA INPUTS
89. DATA INPUTS
90. DATA INPUTS class Person def nickname nick end end
91. def render_details(person) content_tag(:h1, person.name) + \ content_tag(:h2, person.nickname) end DATA INPUTS class Person def nickname nick end end
92. def render_details(person) content_tag(:h1, person.name) + \ content_tag(:h2, person.nickname) end DATA INPUTS class Person def nickname nick end end class Person def nickname nick || first_name end end def render_details(person) content_tag(:h1, person.name) + \ content_tag(:h2, person.nickname) end
93. Bundled together! DATA INPUTS
94. class Plot def draw_line(x1,y1,x2,y2) # do something end def draw_triangle(a1,b1, a2,b2, a3,b3) # do something end end DATA INPUTS
95. DATA INPUTS
96. DATA INPUTS point = Struct.new(:x, :y)
97. DATA INPUTS class Line def initialize(pointX, pointY) end end class Triangle def initialize(pointX, pointY, pointZ) end end point = Struct.new(:x, :y)
98. DATA INPUTS class Line def initialize(pointX, pointY) end end class Triangle def initialize(pointX, pointY, pointZ) end end point = Struct.new(:x, :y) class Plot def draw_line(Line.new(pointX, pointY)) end def draw_triangle(Triangle.new(pointX, pointY, pointZ)) end end
99. “Be conservative in what you send, be liberal in what you accept.” Postel's Law
100. https://theemptypage.files.wordpress.com/2013/04/kitten-at-computer.jpg
101. Total functions RETURNING DATA
102. def search(hash_params) results = SearchModel.search(hash_params) if results.nil? return nil else case results.size when 0 0 when 1 results.first.to_json else results.collect{|x| x.to_json} end end end RETURNING DATA
103. GET /stores/{store_hash}/v2/blog/posts [ { "id": 2, "title": "Ten Great New Products", "url": "/blog/ten-great-new-products/", "body": "<p>Here's ten new products that make great gifts...</ p>", "summary": "Here's ten new products that make great gifts...", "author": "Clary Johnson" }, { "id": 3, "title": "The Laughing Monsters: A Novel", "url": "/blog/laughing-monsters-a-novel/", "body": "<p>Denis Johnson's The Laughing Monsters is a high- suspense tale</p>", "summary": "Denis Johnson's The Laughing Monsters is a high- suspense tale", "author": "Denis Johnson" }, ] RETURNING DATA
104. def search(hash_params) results = SearchModel.search(hash_params) results.collect{|x| x.to_json} end RETURNING DATA
105. Graceful exit RETURNING DATA
106. RETURNING DATA
107. def create_profile(attributes) unless @banned # do something else otherwise end end RETURNING DATA
108. def create_profile(attributes) unless @banned # do something else otherwise end end RETURNING DATA
109. def create_profile(attributes) unless @banned # do something else otherwise end end def create_profile(attributes) return if @banned # do something else otherwise end RETURNING DATA
110. http://www.programmableweb.com/wp-content/cat-can-fix.jpg
111. You throw, I’ll catch ERROR HANDLING
112. ERROR HANDLING https://rubymonk.com/learning/books/4-ruby-primer-ascent/ chapters/41-exceptions/lessons/93-throw-and-catch
113. floor = [["blank", "blank", "blank"], ["gummy", "blank", "blank"], ["blank", "blank", "blank"]] attempts = 0 candy = nil catch(:found) do floor.each do |row| row.each do |tile| attempts += 1 if tile == "jawbreaker" || tile == "gummy" candy = tile throw(:found) end end end end ERROR HANDLING https://rubymonk.com/learning/books/4-ruby-primer-ascent/ chapters/41-exceptions/lessons/93-throw-and-catch
114. floor = [["blank", "blank", "blank"], ["gummy", "blank", "blank"], ["blank", "blank", "blank"]] attempts = 0 candy = nil catch(:found) do floor.each do |row| row.each do |tile| attempts += 1 if tile == "jawbreaker" || tile == "gummy" candy = tile throw(:found) end end end end ERROR HANDLING puts candy # => gummy puts attempts # => 4 https://rubymonk.com/learning/books/4-ruby-primer-ascent/ chapters/41-exceptions/lessons/93-throw-and-catch
115. ERROR HANDLING https://rubymonk.com/learning/books/4-ruby-primer-ascent/ chapters/41-exceptions/lessons/93-throw-and-catch
116. floor = [["blank", "blank", "blank"], ["gummy", "blank", "blank"], ["blank", "blank", "blank"]] attempts = 0 candy = catch(:found) do floor.each do |row| row.each do |tile| attempts += 1 throw(:found, tile) if tile == "jawbreaker" || tile == "gummy" end end end ERROR HANDLING https://rubymonk.com/learning/books/4-ruby-primer-ascent/ chapters/41-exceptions/lessons/93-throw-and-catch
117. floor = [["blank", "blank", "blank"], ["gummy", "blank", "blank"], ["blank", "blank", "blank"]] attempts = 0 candy = catch(:found) do floor.each do |row| row.each do |tile| attempts += 1 throw(:found, tile) if tile == "jawbreaker" || tile == "gummy" end end end ERROR HANDLING puts candy # => gummy puts attempts # => 4 https://rubymonk.com/learning/books/4-ruby-primer-ascent/ chapters/41-exceptions/lessons/93-throw-and-catch
118. No beginning, no end ERROR HANDLING
119. ERROR HANDLING
120. begin # - rescue OneTypeOfException # - rescue AnotherTypeOfException # - else # Other more general exceptions ensure # Always will be executed end ERROR HANDLING
121. ERROR HANDLING def your_buggy_method begin do_work1 rescue Exception do_rescue_1 end begin do_work_2 rescue Exception do_rescue_1 end end
122. ERROR HANDLING
123. Solution #1: ERROR HANDLING
124. def your_buggy_method do_work1_method do_work_2_method end def do_work_1_method do_work1 rescue Exception e do_rescue_1 end def do_work_2_method do_work2 rescue Exception e do_rescue_2 end Solution #1: ERROR HANDLING
125. def your_buggy_method do_work1_method do_work_2_method end def do_work_1_method do_work1 rescue Exception e do_rescue_1 end def do_work_2_method do_work2 rescue Exception e do_rescue_2 end Solution #1: ERROR HANDLING Solution #2:
126. def your_buggy_method do_work1_method do_work_2_method end def do_work_1_method do_work1 rescue Exception e do_rescue_1 end def do_work_2_method do_work2 rescue Exception e do_rescue_2 end Solution #1: ERROR HANDLING Solution #2: def your_buggy_method do_work1 rescue Exception e do_rescue_1 do_work2 rescue Exception e do_rescue_2 end
127. • Confident Ruby: 32 Patterns for Joyful Coding by Avdi Grimm • Exceptional Ruby: Master the Art of Handling Failure in Ruby by Avdi Grimm • Eloquent Ruby by Russ Olsen • Effective Ruby: 48 Specific Ways to Write Better Ruby by Peter J. Jones Further Readings
128. http://www.virgin.com/sites/default/files/legacy/storytelling-18642.jpg