Ruby is Magic: Cupcakes

This episode is mainly about the use of enumerators in Ruby. The slides are in German but the code snippets maybe useful to you.

Copyright Notice: My Little Pony - Friendship is Magic is Property of Hasbro and The Hub.

Transcript

1. Brony User Group Cologne hosted by 21.11.2012
2. Ruby #12 Cupcakes
3. Lecker Was für Zwischendurch Klein
6. Wir brauchen 20% mehr Structur!
7. Struct.new("Pony", :name, :type) # => Struct::Pony applejack = Struct::Pony.new("Applejack", "Earth Pony") # => #<struct Struct::Pony name="Applejack", type="Earth Pony">
8. class end # => Pony applejack = Pony.new("Applejack", "Earth Pony") # => #<struct Pony name="Applejack", type="Earth Pony"> Pony < Struct.new(:name, :type)
9. ??? Pony < Struct.new(:name, :type)
10. class MyStruct def self.new(*attr_names) Class.new do attr_accessor(*attr_names) def initialize(*attributes) self.class.instance_methods.grep(/.*=$/).each do |m| send(m, attributes.shift) end end end end end
11. class Pony < MyStruct.new(:name, :type) end rainbow_dash = Pony.new("Rainbow Dash", "Pegasus") # => #<Pony:0x007f995d083150 @name="Rainbow Dash", @type="Pegasus">
12. Pony = Struct.new(:name, :type)
13. Aber Warum?!
14. Weil wir es können…
15. …und für “Domain Concepts”* *Steve Klabnik
16. class Pony attr_reader :name, :street, :street_number, :zip, :city def initialize(opts) @name = opts[:name] @street = opts[:street] @street_number = opts[:street_number] @zip = opts[:zip] @city = opts[:city] end end
17. class Pony attr_reader :name, :address Address = Struct.new(:street, :street_number, :zip, :city) def initialize(opts) @name = opts[:name] @address = Address.new(opts[:street], opts[:street_number], opts[:zip], opts[:city]) end end
18. OpenStruct
19. Container für Konfiguration
20. require 'ostruct' config = OpenStruct.new config.environment = "development" config.cache_store = "redis://127.0.0.1:6379" config.logger = STDOUT config.time_zone = "Europe/Berlin" p config # => #<OpenStruct environment="development", # cache_store="redis://127.0.0.1:6379", # logger=#<IO:<STDOUT>>, # time_zone="Europe/Berlin">
21. ActiveSupport::OrderedOptions
22. Sequenzen
23. “a particular order in which related events, movements, or things follow each other.” A sequence is…
24. Schon mal verwendet?
25. sequence.next # 1 sequence.next # 2 sequence.next # 3 sequence.next # 4 sequence.next # 5 ...
26. row_type.next # odd row_type.next # even row_type.next # odd row_type.next # even row_type.next # odd ...
27. names.next # Fluttershy names.next # Applejack names.next # Rainbow Dash names.next # Pinkie Pie names.next # Twighlight Sparkle names.next # Rarity
28. Enumerator
29. row_type = %w(odd even).cycle
30. names = ["Fluttershy", "Applejack", "Rainbow Dash", "Pinkie Pie", "Twighlight Sparkle", "Rarity"].each
31. sequence = Enumerator.new do |yielder| number = 0 loop do number += 1 yielder.yield number end end
32. #next #rewind #peek #feed #each
33. Alles hat ein Ende…
34. … names.next # Pinkie Pie names.next # Twighlight Sparkle names.next # Rarity names.next sequence.rb:46:in `next': iteration reached an end (StopIteration) ! from sequence.rb:46:in `<main>'
35. class List def initialize(elements) @elements = elements end def each(&block) build_each(@elements.to_enum, &block) end def build_each(enum) while true begin next_value = enum.next yield next_value rescue StopIteration => iterator return iterator.result end end end end list = List.new [1,2,3,4] p list.each { |i| puts i }
36. Fun Fact loop do … end Fängt IMMER die StopIteration Exception
37. class List def initialize(elements) @elements = elements end def each(&block) build_each(@elements.to_enum, &block) end def build_each(enum) loop do yield enum.next end enum.to_a # Needed to make both versions equivalent end end list = List.new [1,2,3,4] p list.each { |i| puts i }
38. Alles hat ein Ende?
39. sequence = Enumerator.new do |yielder| number = 0 loop do number += 1 yielder.yield number end end Endlosschleife?! What in tarnation?
42. require "fiber" sequence = Fiber.new do number = 0 loop do number += 1 Fiber.yield number end end def sequence.next resume end
43. Lazy Enumerations
44. class Sequencer def initialize @start = 0 end def each loop do @start += 1 yield @start end end end
45. seq = Sequencer.new.to_enum ten_above_100 = [] while true n = seq.next ten_above_100 << n if n > 100 break if ten_above_100.size == 10 end p ten_above_100 # => [101, 102, 103, 104, 105, 106, 107, 108, 109, 110]
46. seq.select { |x| x > 100 }.take(10) Endet nie…
47. Ruby 2.0 Feature
48. seq = Sequencer.new.to_enum p seq.lazy.select { |x| x > 100 }.take(10).to_a # => [101, 102, 103, 104, 105, 106, 107, 108, 109, 110]
49. Structs sind praktisch, um “Domain Concepts” zu verpacken Wir benutzen ständig Sequenzen in Ruby Wenn erforderlich, können wir uns leicht infinite Sequenzen bauen
50. One More Thing…
52. <Insert Shameless Plug here!>
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55. http://home-office-cologne.de
56. Thanks! Q & A? Dirk Breuer / @railsbros_dirk Sebastian Cohnen / @tisba ? “My Little Pony” © Hasbro Studios and DHX Media Vancouver rubyismagic.de
57. Just for Jakob…
58. Kapseln den Ausführungskontext Erhalten Zugriff auf Variablen, Methoden, self Werden erzeugt mit Kernel#binding
59. class Pony def say_hello(a_binding = nil) eval('puts "Hello, my name is #{@name}"', a_binding || binding) end end somepony = Pony.new somepony.say_hello # Hello, my name is @name = "Rainbow Dash" somepony.say_hello(binding) # Hello, my name is Rainbow Dash @name = "Applejack" somepony.say_hello(binding) # Hello, my name is Applejack
60. Okay …
61. … ERB!
62. require 'erb' class View def friend "Pinkie Pie" end def get_binding binding end end template = ERB.new <<-ERB Welcome to Ruby is Magic! Let me introduce you to my good friend <%= friend %>. ERB puts template.result # (erb):3:in `<main>': undefined local variable or method `friend' for main:Object # from /lib/ruby/1.9.1/erb.rb:838:in `eval' # from /lib/ruby/1.9.1/erb.rb:838:in `result' # from Ruby is Magic.rb/011-clip-show/code/erb_demo.rb:19:in `<main>' puts template.result(View.new.get_binding) # Let me introduce you to my good friend Pinkie Pie.