Ruby's Inner Beauty

My presentation for the March Columbus Ruby Brigade meeting on Ruby syntax & semantics.

1. RUBY'S INNER BEAUTY ALEX BURKHART - @SATERUS
2. SYNTAX
3. SYNTAX VS SEMANTICS
4. SEMANTICS VS IMPLEMENTATION
5. INTERPRETED
6. PARSING VS EXECUTION
7. PARSE A LINE 2 + 5 * 10 2 + (5 * 10) (2 + (5 * 10))
8. EVALUATE THE EXPRESSION TREE 2 + 5 * 10 2 + (5 * 10) (2 + (5 * 10)) (2 + (50)) (2 + 50) (52) 52
9. RUBY'S PARSER TRICKS
10. HUMAN READABLE NUMBERS error_prone = 1000000000 super_easy = 1_000_000_000 if error_prone != super_easy raise ProgrammerError.new("Looks like you made a typo!") end
11. SHORTHAND SYNTAX square = Proc.new { |x| x * x } square.call(2) # => 4 cube = ->(y){ y * y * y } cube.call(2) # => 8 cube.class == Proc # => true
12. ARRAY SYNTAX a1 = [1,2,3] a2 = Array.new(1,2,3) a1 == a2 # => true
13. HASH SYNTAX h1 = { a: 10 } h2 = { :a => 10 } h3 = Hash.new h3[:a] = 10 h1 == h2 == h3 # => true
14. STRING SYNTAX s1 = "syntactic" s2 = 'syntactic' s3 = String.new("syntactic") s1 == s2 == s3 # => true
15. ARRAY OF * SYNTAX words1 = %w| array of strings | words2 = ["array", "of", "strings"] sym1 = %i( array of symbols ) sym2 = [:array, :of, :symbols]
16. FAKE SYNTAX params = { category: 'ruby' } params[:category] # => 'ruby'
17. FAKE SYNTAX params = { category: 'ruby' } params[:category] # => 'ruby' class Hash def [](key) fetch(key, nil) end end
18. INSTANCE VARIABLE ACCESS class Coffee def initialize(size, roast) @size = size @roast = roast end def to_s "#{@size} cup of #{@roast} roast" end end pry> Coffee.new('large', 'light').to_s => "large cup of light roast"
19. INSTANCE VARIABLE ACCESS class Coffee def initialize(size, roast) instance_variable_set(:@size, size) instance_variable_set(:@roast, roast) end def to_s size = instance_variable_get(:@size) roast = instance_variable_get(:@roast) "#{size} cup of #{roast} roast" end end pry> Coffee.new('large', 'light').to_s => "large cup of light roast"
20. BasicObject#send
21. MESSAGE PASSING cup = Coffee.new('large', 'light') cup.to_s == cup.send(:to_s)
22. MESSAGE PASSING W/ ARGS client = ApiClient.new client.get('/foo', page: 2) client.send(:get, '/foo', { page: 2 })
23. EVERYTHING IS A MESSAGE 12 + 8 12.send(:+, 8) operators = [:+, :-, :/] operators.send(:<<, :*)
24. ASSIGNMENT class Todo attr_accessor :state def initialize(title) @title = title @state = :pending end end ruby_talk = Todo.new("Present Ruby's Inner Beauty at CRB") ruby_talk.state = :in_progress
25. ASSIGNMENT METHODS class Todo attr_reader :state def initialize(title) @title = title @state = :pending end def state=(state) @state = state end end ruby_talk = Todo.new("Present Ruby's Inner Beauty at CRB") ruby_talk.state = :in_progress
26. ASSIGNMENT METHODS class Todo attr_reader :state def initialize(title) @title = title @state = :pending end def state=(state) @state = state end end ruby_talk = Todo.new("Present Ruby's Inner Beauty at CRB") ruby_talk.state=(:in_progress)
27. ASSIGNMENT VIA MESSAGES class Todo attr_reader :state def initialize(title) @title = title @state = :pending end def state=(state) @state = state end end ruby_talk = Todo.new("Present Ruby's Inner Beauty at CRB") ruby_talk.send(:state=, :in_progress)
28. ABSOLUTELY EVERYTHING IS A MESSAGE class Todo attr_reader :state def initialize(title) @title = title @state = :pending end def state=(state) @state = state end end ruby_talk = Todo.send(:new, "Present Ruby's Inner Beauty at CRB") ruby_talk.send(:state=, :in_progress)
29. Class#new class Class def new(*args) instance = allocate instance.initialize(*args) instance end def allocate Heap.malloc(self) # gross simplification end end Coffee.send(:new, 'medium', 'dark')
30. Class#new IS JUST A METHOD
31. include Celluloid # Class methods added to classes which include Celluloid module ClassMethods # Create a new actor def new(*args, &block) proxy = Cell.new(allocate, behavior_options, actor_options).proxy proxy._send_(:initialize, *args, &block) proxy end end
32. ASYNC MESSAGE PASSING class AsyncSpammer include Celluloid def deliver_spam(address) sleep(1) puts "spamming #{address.inspect}" end end worker = AsyncSpammer.new # => #<Celluloid::CellProxy(AsyncSpammer:0x3fd351810484)> worker.async.deliver_spam('your_email@example.com') # => nil # => spamming "your_email@example.com"
33. THAT'S PRETTY CLASSY
34. class KEYWORD class Todo def initialize(title) @title = title @state = :pending end def to_s "#{@state}: #{@title}" end end Todo.new('Introduce class Keyword')
35. Class::new
36. Class::new Todo = Class.new(Object) do def to_s "#{@state}: #{@title}" end end Todo.send(:new, "Reveal the `new` class method on Class")
37. REOPENING CLASSES Todo ||= Class.new(Object) Todo.class_eval do def state=(state) instance_variable_set(@:state, state) end end t2 = Todo.send(:new, 'Reopen Todo Class') t2.send(:state=, :in_progress)
38. WHAT THE def?
39. def DEMYSTIFIED class Todo define_method(:state=) do |new_state| @state = new_state end end t2 = Todo.new('Breakdown def keyword') t2.state = :in_pieces
40. def DEMYSTIFIED Todo ||= Class.new Todo.class_eval do define_method :state= do |new_state| instance_variable_set(:@state, new_state) end end t2 = Todo.send(:new, 'Breakdown def keyword') t2.send(:state=, :in_pieces)
41. attr_reader attr_writer attr_accessor
42. A BETTER METHOD MAKING MACHINE Class.class_eval do define_method(:bttr_reader) do |name| define_method(name) do instance_variable_get("@#{name}") end end end Todo.class_eval { bttr_reader :title } t = Todo.new("Reimplement attr_reader") t.title # => "Reimplement attr_reader"
43. PRACTICALLY A MONEY MAKING MACHINE Class.class_eval do define_method(:bttr_writer) do |name| define_method("#{name}=") do |val| instance_variable_set("@#{name}", val) end end end Todo.class_eval { bttr_writer :title } t = Todo.new("Reimplement attr_writer") t.title = "A much better writer..." t.title # => "A much better writer..."
44. PRIVATE METHODS class TodoList def to_s unfinished_tasks.join("\n") end private def unfinished_tasks @todos.reject(&:completed?) end end
45. MODULE PUBLICITY Module#define_method(name, &impl) => sym Module#public(*syms) Module#protected(*syms) Module#private(*syms)
46. PRIVATE METHODS TodoList ||= Class.new TodoList.class_eval do private( define_method(:unfinished_tasks) do @todos.reject(&:completed?) end ) end
47. RECEIVERLESS METHODS class MonthlyReport def print_as_table puts header rows.each do |row| puts row end puts footer end end
48. KERNEL module Kernel def puts(strs*) # ... end end Object.include(Kernel)
49. LOCAL VARIABLES class Todo def state=(new_state) previous_state = @state puts "Transitioning from #{previous_state} to #{new_state}" @state = new_state end end
50. Kernel#binding class Todo def state=(new_state) previous_state = @state binding.local_variables # => [:new_state, :previous_state] puts "Transitioning from #{previous_state} to #{new_state}" binding.eval('new_state') == new_state # => true @state = new_state end end
51. LOCAL VARIABLES ARE SYNTAX SHORTCUTS! class Todo def state=(new_state) @state = binding.local_variable_get(:new_state) end end
52. REMOVING THE SYNTAX Todo.class_eval do define_method :state= do |new_state| instance_variable_set(:@state, binding.local_variable_get(:new_state)) end end
53. LOCAL CONTEXT
54. SELF class Todo def get_binding binding end def get_self binding.eval('self') end end t = Todo.new t.get_binding # => #<Binding:0x007fa6a485df20> t.get_self # => #<Todo:0x007fa6a485df20>
55. CHANGE SELF Todo.class_eval do # self == Todo class end t2 = Todo.new("Change execution contexts") t2.instance_eval do # self == instance of Todo end
56. SELF IS THE END
57. SMALL LANGUAGE
58. SYNTAX VS SEMANTICS
59. ELEGANCE
60. RUBY IS BEAUTIFUL
61. SHAMELESS PLUG FOR Mutually Human MUTUALLYHUMAN.COM
62. SHAMEFUL PLUG FOR COLUMBUS RUST SOCIETY @COLUMBUSRUST
63. THANKS! ALEX BURKHART @SATERUS Mutually Human