The Fun in Functional

Functional programming is all the rage these days, and many Rubyists feel left out of all the fun. But don't despair - many of the great ideas that are coming out of the functional revolution are applicable to our Ruby code, too! In this talk we'll explore some of the ways we can make our Ruby code more functional (pun intended) without giving up any of the joys of object orientation. In this talk you'll see how using some functional programming concepts can make your Ruby code easier to test, easier to maintain, and easier to change!

Transcript

1. The Fun in Functional Devon Estes @devoncestes github.com/devonestes
4. Warning! ⚠
5. Warning! ⚠ I’m going to try and be funny
6. “First, make the change easy (warning: this may be hard), then make the easy change.” - Kent Beck
7. “First, become Aaron Patterson or Justin Searls (warning: this may be hard), then write the presentation.” - Me
9. &
10. )
18. Ruby, we have a problem…
19. Moore’s Law
20. Speed Complexity
21. Moore’s Law is Dead ☠
22. Moore’s Law is Dead ☠ (to Ruby)
23. Moore’s Law is Dead ☠ (to Ruby) (and by Ruby, I mean MRI)
25. Functional Programming to the Rescue!
26. Functional Programming to the Rescue! Immutable data structures
27. Functional Programming to the Rescue! Immutable data structures Lazy or delayed evaluation
28. Functional Programming to the Rescue! Immutable data structures Lazy or delayed evaluation Pure functions
29. Functional Programming to the Rescue! Immutable data structures Lazy or delayed evaluation Pure functions Higher order functions
30. Functional Programming to the Rescue! Immutable data structures Lazy or delayed evaluation Pure functions Higher order functions Curried functions
31. Functional Programming to the Rescue! Immutable data structures Lazy or delayed evaluation Pure functions Higher order functions Curried functions
32. Ruby to the Rescue!
33. Ruby to the Rescue! Immutable data structures
34. Ruby to the Rescue! Immutable data structures Lazy or delayed evaluation
35. Ruby to the Rescue! Immutable data structures Lazy or delayed evaluation Pure functions
36. Ruby to the Rescue! Immutable data structures Lazy or delayed evaluation Pure functions Higher order functions
37. Ruby to the Rescue! Immutable data structures Lazy or delayed evaluation Pure functions Higher order functions Curried functions
38. Ruby - The Language of the Future
39. I ❤ # => ruby client.rb data_for_team 'New York Jets' # # => ruby client.rb data_for_game 'New York Jets' 'Miami Dolphins' '11/06/2016' # client = NFLData::Client.new(api_key: ENV['NFL_API_KEY']) case ARGV[0] when 'data_for_team' puts client.data_for_team(team_name: ARGV[1]) when 'data_for_game' puts client.data_for_game(team1: ARGV[1], team2: ARGV[2], date: ARGV[3]) else 'Not a recognized command' end
40. module NFLData class Client def initialize(api_key:) @api_key = api_key end def data_for_team(team_name:) url = "http://nfl.com/api/v1/teams/#{team_name}?api_key=#{api_key}" raw = fetch_raw_data(url) add_turnover_data(raw) add_win_percentage(raw) add_how_team_is_doing(raw) end def data_for_game(team1:, team2:, date:) url = “http://nfl.com/api/v1/games/#{date}?teams=#{team1},#{team2} &api_key=#{api_key}" raw = fetch_raw_data(url) add_rushing_comparison(raw) add_passing_comparison(raw) end private # ...
41. private attr_reader :api_key def fetch_raw_data(url) uri = URI.parse(url) json = Net::HTTP.get(uri) JSON.parse(json) end def add_turnover_data(raw) raw[:turnover_differential] = raw[:num_defensive_turnovers].to_i - raw[:num_offensive_turnovers].to_i end def add_win_percentage(raw) total_games = raw[:num_wins] + raw[:num_losses] raw[:win_percentage] = raw[:num_wins].to_f / total_games.to_f end def add_how_team_is_doing(raw) def add_rushing_comparison(raw) def add_passing_comparison(raw) end end
42. module NFLData class Client def initialize(api_key:) @api_key = api_key end def data_for_team(team_name:) url = "http://nfl.com/api/v1/teams/#{team_name}?api_key=#{api_key}" raw = fetch_raw_data(url) add_turnover_data(raw) add_win_percentage(raw) add_how_team_is_doing(raw) end def data_for_game(team1:, team2:, date:) url = “http://nfl.com/api/v1/games/#{date}?teams=#{team1},#{team2} &api_key=#{api_key}" raw = fetch_raw_data(url) add_rushing_comparison(raw) add_passing_comparison(raw) end private # ...
43. module NFLData class Client def initialize(api_key:) @api_key = api_key end def data_for_team(team_name:) url = "http://nfl.com/api/v1/teams/#{team_name}?api_key=#{api_key}" raw = fetch_raw_data(url) add_turnover_data(raw) add_win_percentage(raw) add_how_team_is_doing(raw) end def data_for_game(team1:, team2:, date:) url = “http://nfl.com/api/v1/games/#{date}?teams=#{team1},#{team2} &api_key=#{api_key}" raw = fetch_raw_data(url) add_rushing_comparison(raw) add_passing_comparison(raw) end private # ...
44. team_client = NFLData::Team.new(api_key: ENV['NFL_API_KEY']) game_client = NFLData::Game.new(api_key: ENV['NFL_API_KEY']) case ARGV[0] when 'data_for_team' puts team_client.get_data(team_name: ARGV[1]) when 'data_for_game' puts game_client.get_data(team1: ARGV[1], team2: ARGV[2], date: ARGV[3]) else 'Not a recognized command' end
45. module NFLData class Base def initialize(api_key:) @api_key = api_key end private attr_reader :api_key def fetch_raw_data(url) uri = URI.parse(url) json = Net::HTTP.get(uri) JSON.parse(json) end end end
46. module NFLData class Game < NFLData::Base def get_data(team1:, team2:, date:) url = “http://nfl.com/api/v1/games/#{date}?teams=#{team1},#{team2} &api_key=#{api_key}" @raw = fetch_raw_data(url) add_rushing_comparison add_passing_comparison add_defensive_comparison end private attr_reader :raw def add_rushing_comparison def add_passing_comparison def add_defensive_comparison end end
47. module NFLData class Team < NFLData::Base def get_data(team_name:) url = "http://nfl.com/api/v1/teams/#{team_name}?api_key=#{api_key}" @raw = fetch_raw_data(url) add_turnover_data add_win_percentage add_how_team_is_doing end private attr_reader :raw def add_turnover_data def add_win_percentage def add_how_team_is_doing end end
50. module NFLData class Game < NFLData::Base def get_data(team1:, team2:, date:) url = “http://nfl.com/api/v1/games/#{date}?teams=#{team1},#{team2} &api_key=#{api_key}" @raw = fetch_raw_data(url) add_rushing_comparison add_passing_comparison add_defensive_comparison end private attr_reader :raw def add_rushing_comparison def add_passing_comparison def add_defensive_comparison end end
51. module NFLData class Game < NFLData::Base def get_data(team1:, team2:, date:) url = “http://nfl.com/api/v1/games/#{date}?teams=#{team1},#{team2} &api_key=#{api_key}" @raw = fetch_raw_data(url) add_rushing_comparison add_passing_comparison add_defensive_comparison end private attr_reader :raw def add_rushing_comparison def add_passing_comparison def add_defensive_comparison end end
52. module NFLData class Base def initialize(api_key:, fetcher:) @api_key = api_key @fetcher = fetcher end private attr_reader :api_key, :fetcher end end
53. module NFLData class Game < NFLData::Base def call(team1:, team2:, date:) url = "http://nfl.com/api/v1/games/#{date}?teams=#{team1},#{team2} &api_key=#{api_key}" @raw = fetcher.call(url) add_rushing_comparison add_passing_comparison add_defensive_comparison end private attr_reader :raw def add_rushing_comparison def add_passing_comparison def add_defensive_comparison end end
54. irb(main):001:0> l = ->(str) { puts str.upcase } irb(main):002:0> l.call('hi') HI nil irb(main):003:0> str = 'hi' irb(main):004:0> p = Proc.new { puts str.upcase } irb(main):005:0> p.call HI nil irb(main):006:0> def up(str) irb(main):007:1> puts str.upcase irb(main):008:1> end :up irb(main):009:0> m = method(:up) Object#upp(str) irb(main):010:0> m.call('hi') HI nil irb(main):011:0> def call_block(&block) irb(main):012:1> block.call('hi') irb(main):013:1> end :call_block irb(main):014:0> call_block { |str| puts str.upcase } HI nil
56. fetcher = -> (url) do uri = URI.parse(url) json = Net::HTTP.get(uri) JSON.parse(json) end team_client = NFLData::Team.new(api_key: ENV['NFL_API_KEY'], fetcher: fetcher) game_client = NFLData::Game.new(api_key: ENV['NFL_API_KEY'], fetcher: fetcher) case ARGV[0] when 'data_for_team' puts team_client.get_data(team_name: ARGV[1]) when 'data_for_game' puts game_client.get_data(team1: ARGV[1], team2: ARGV[2], date: ARGV[3]) else 'Not a recognized command' end
57. client = NFLData::Client.new(api_key: ENV['NFL_API_KEY']) case ARGV[0] when 'data_for_team' puts client.data_for_team(team_name: ARGV[1]) when 'data_for_game' puts client.data_for_game(team1: ARGV[1], team2: ARGV[2], date: ARGV[3]) else 'Not a recognized command' end
58. module NFLData class Client def initialize(api_key:) @api_key = api_key end def data_for_team(team_name:) url = "http://nfl.com/api/v1/teams/#{team_name}?api_key=#{api_key}" raw = fetch_raw_data(url) add_turnover_data(raw) add_win_percentage(raw) add_how_team_is_doing(raw) end def data_for_game(team1:, team2:, date:) url = “http://nfl.com/api/v1/games/#{date}?teams=#{team1},#{team2} &api_key=#{api_key}" raw = fetch_raw_data(url) add_rushing_comparison(raw) add_passing_comparison(raw) end private # ...
59. The Method Object
60. module NFLData class Client def initialize(api_key:, fetcher: default_fetcher) @api_key = api_key @fetcher = fetcher end def data_for_team(team_name:) url = "http://nfl.com/api/v1/teams/#{team_name}?api_key=#{api_key}" NFLData::Team.new(fetcher: fetcher).call(url: url) end def data_for_game(team1:, team2:, date:) url = “http://nfl.com/api/v1/games/#{date}?teams=#{team1},#{team2} &api_key=#{api_key}" NFLData::Game.new(fetcher: fetcher).call(url: url) end private attr_reader :api_key, :fetcher def default_fetcher end end
61. module NFLData class Game def initialize(fetcher:) @fetcher = fetcher end def call(url:) @data = fetcher.call(url) add_rushing_comparison add_passing_comparison add_defensive_comparison data end private attr_reader :fetcher, :data def add_rushing_comparison def add_passing_comparison def add_defensive_comparison end end
62. module NFLData class Team def initialize(fetcher:) @fetcher = fetcher end def call(url:) @data = fetcher.call(url) add_turnover_data add_win_percentage add_how_team_is_doing data end private attr_reader :fetcher, :data def add_turnover_data def add_win_percentage def add_how_team_is_doing end end
63. Pure Function
64. Pure Function 1) Same output for a given input ⚖
65. Pure Function 1) Same output for a given input ⚖ 2) No side effects
66. Pure Function Benefits
67. Pure Function Benefits Super easy to test
68. Pure Function Benefits Super easy to test Super easy to make thread safe
69. Pure Function Benefits Super easy to test Super easy to make thread safe Highly composable
70. Is it Pure?
71. IO#read irb(main):001:0> IO.read('call.rb') "irb(main):001:0> l = ->(str) #..."
72. IO#read irb(main):001:0> IO.read('call.rb') "irb(main):001:0> l = ->(str) #..." irb(main):002:0> IO.read('call.rb') Errno::ENOENT: No such file or directory @ rb_sysopen - call.rb from (irb):2:in 'read' from (irb):2 from /Users/devoncestes/.rbenv/versions/2.3.1/bin/irb:11:in '<main>'
73. Integer#+ irb(main):001:0> 2 + 2 4
74. Integer#+ irb(main):001:0> 2 + 2 4 irb(main):002:0> 2 + 2 4
75. Integer#+ irb(main):001:0> 2 + 2 4 irb(main):002:0> 2 + 2 4 irb(main):003:0> 2 + 2 4
76. String#downcase irb(main):001:0> str = 'I am a String' "I am a String"
77. String#downcase irb(main):001:0> str = 'I am a String' "I am a String" irb(main):002:0> str.downcase "i am a string"
78. String#downcase irb(main):001:0> str = 'I am a String' "I am a String" irb(main):002:0> str.downcase "i am a string" irb(main):003:0> str "I am a String"
79. String#<< irb(main):001:0> str = 'Is << pure?' "Is << pure?"
80. String#<< irb(main):001:0> str = 'Is << pure?' "Is << pure?" irb(main):002:0> str << " Let's find out!" "Is << pure? Let's find out!"
81. String#<< irb(main):001:0> str = 'Is << pure?' "Is << pure?" irb(main):002:0> str << " Let's find out!" "Is << pure? Let's find out!" irb(main):003:0> str "Is << pure? Let's find out!"
82. client = NFLData::Client.new(api_key: ENV['NFL_API_KEY']) case ARGV[0] when 'team_data' puts client.team_data(team_name: ARGV[1]) when 'game_data' puts client.game_data(team1: ARGV[1], team2: ARGV[2], date: ARGV[3]) else 'Not a recognized command' end
83. module NFLData class Client def initialize(api_key:, fetcher: default_fetcher) @api_key = api_key @fetcher = fetcher end def team_data(team_name:, metadata_adder: NFLData::Metadata::Team) url = "http://nfl.com/api/v1/teams/#{team_name}?api_key=#{api_key}" data = fetcher.call(url) metadata_adder.call(data: data) end def game_data(team1:, team2:, date:, metadata_adder: NFLData::Metadata::Game) url = “http://nfl.com/api/v1/games/#{date}?teams=#{team1},#{team2} &api_key=#{api_key}" data = fetcher.call(url) metadata_adder.call(data: data) end private attr_reader :api_key, :fetcher def default_fetcher end end
84. module NFLData module Metadata class Team def self.call(**args) new(args).call end def initialize(data:) @data = data end def call add_turnover_data add_win_percentage add_how_team_is_doing data.freeze end private attr_reader :data # ... end end end
85. module NFLData module Metadata class Game def self.call(**args) new(args).call end def initialize(data:) @data = data end def call add_rushing_comparison add_passing_comparison add_defensive_comparison data.freeze end private attr_reader :data # ... end end end
88. Takeaways
89. Takeaways Method objects are your friend
90. Takeaways Method objects are your friend Avoid the mystery guest
91. Takeaways Method objects are your friend Avoid the mystery guest Look for pure functions ✨
92. Takeaways Method objects are your friend Avoid the mystery guest Look for pure functions ✨ Delay and group side effects
93. Takeaways Method objects are your friend Avoid the mystery guest Look for pure functions ✨ Delay and group side effects Start thinking about the future
94. Grazie mille per l'ascolto! Chi ha domande?