method_missingの黒魔術っぷりについて

Ebisu.rb #21での発表資料

1. method_missingͷࠇຐज़ͬ΀Γʹ͍ͭͯ 2019/1/29 Ebisu.rb #21 גࣜձࣾΧΧΫίϜ ৯΂ϩάγεςϜຊ෦ ϚΠΫϩαʔϏεԽνʔϜ ௕ాɹᠳ
2. Copyright © Kakaku.com Inc. All Rights Reserved. ࣗݾ঺հ ௕ాɹᠳʢͳ͕ͨɹ͠ΐ͏ʣ • మಓܥSIerͰSEΛ7೥൒ • 2018೥9݄ʹΧΧΫίϜೖࣾ • όοΫΤϯυΤϯδχΞͱͯ͠৯΂ϩάͷϚΠΫϩαʔϏε ԽΛਪਐத • Ruby / Railsྺ͸5ϲ݄ • ݸਓతʹMachine Learning΍Blockchain৮ͬͨΓ • ޷͖ͳݴޠ͸Python • Ϛϥιϯ΍ͬͨΓΪλʔ΍ͬͨΓғޟ΍ͬͨΓ • 2ࣇͷ෕ ˏs_naga03 Sho Nagata nagata03
3. Copyright © Kakaku.com Inc. All Rights Reserved. ࠓ೔࿩͢͜ͱ RubyΛ৮Γ࢝Ίͯ1ϲ݄ࠒʹ܁Γ޿͛ͨϝιουఆٛͱͷઓ͍
4. Copyright © Kakaku.com Inc. All Rights Reserved. ࠓ೔࿩͢͜ͱ RubyΛ৮Γ࢝Ίͯ1ϲ݄ࠒʹ܁Γ޿͛ͨϝιουఆٛͱͷઓ͍ ͦ͜Ͱग़ձͬͨ೉ఢ…
5. ࠇຐज़ɿmethod_missing
6. ࠇຐज़ɿmethod_missing
7. Copyright © Kakaku.com Inc. All Rights Reserved. ࢲͷઓಆྗ ઓಆྗɿ1480
8. Copyright © Kakaku.com Inc. All Rights Reserved. ࢲͷઓಆྗ ઓಆྗɿ1480 ʢϕδʔλऻདྷ࣌ʣ ʢDBެࣜʣ
9. ࠇຐज़ɿmethod_missing
10. ࠇຐज़ɿmethod_missing
11. Copyright © Kakaku.com Inc. All Rights Reserved. Rubyྺ1ϲ݄ࠒͷ͜ͱ ݱࡏͷॲཧ಺༰ͷௐࠪ
12. Copyright © Kakaku.com Inc. All Rights Reserved. Rubyྺ1ϲ݄ࠒͷ͜ͱ ݱࡏͷॲཧ಺༰ͷௐࠪ ϝιουΛݕࡧʢϝιου໊Ͱgrepͱ͔ʣ
13. Copyright © Kakaku.com Inc. All Rights Reserved. Rubyྺ1ϲ݄ࠒͷ͜ͱ ݱࡏͷॲཧ಺༰ͷௐࠪ ϝιουΛݕࡧʢϝιου໊Ͱgrepͱ͔ʣ ϝιου͕ݟ͔ͭΓ·ͤΜʂ
14. Copyright © Kakaku.com Inc. All Rights Reserved. Rubyྺ1ϲ݄ࠒͷ͜ͱ ݱࡏͷॲཧ಺༰ͷௐࠪ ϝιουΛݕࡧʢϝιου໊Ͱgrepͱ͔ʣ ϝιου͕ݟ͔ͭΓ·ͤΜʂ ίίʹ͋Γ·͢Αɻ
15. Copyright © Kakaku.com Inc. All Rights Reserved. Rubyྺ1ϲ݄͝Ζͷ͜ͱ def method_missing(…) # … …… end
16. Copyright © Kakaku.com Inc. All Rights Reserved. Rubyྺ1ϲ݄͝Ζͷ͜ͱ ԿॲͰ͔͢ʁ
17. Copyright © Kakaku.com Inc. All Rights Reserved. Rubyྺ1ϲ݄͝Ζͷ͜ͱ ԿॲͰ͔͢ʁ Ͳ͜Ͱ͔͢ʁ
18. Copyright © Kakaku.com Inc. All Rights Reserved. Rubyྺ1ϲ݄͝Ζͷ͜ͱ ԿॲͰ͔͢ʁ Ͳ͜Ͱ͔͢ʁ υίʂʁ
19. Copyright © Kakaku.com Inc. All Rights Reserved. Rubyྺ1ϲ݄͝Ζͷ͜ͱ ԿॲͰ͔͢ʁ Ͳ͜Ͱ͔͢ʁ υίʂʁ ίίˣ def method_missing(…) # … …… end
20. Copyright © Kakaku.com Inc. All Rights Reserved. Rubyྺ1ϲ݄͝Ζͷ͜ͱ
21. Copyright © Kakaku.com Inc. All Rights Reserved. method_missing • BasicObjectΫϥεʹఆٛ͞Ε͍ͯΔprivateͳΠϯελϯεϝιου BasicObject.private_instance_methods.grep(/^method/) => [:method_missing] • ݺͼग़͞Εͨϝιου͕ɺܧঝπϦʔΛḷͬͯ୳ࡧͨ݁͠ՌͲ͜ʹ ΋ఆٛ͞Ε͍ͯͳ͔ͬͨ৔߹ɺmethod_missing͕ݺͼग़͞Ε NoMethodErrorΛൃੜͤ͞Δ
22. Copyright © Kakaku.com Inc. All Rights Reserved. method_missingͷΦʔόʔϥΠυ • method_missingΛΦʔόʔϥΠυ͢Δ͜ͱͰଘࡏ͠ͳ͍ϝιουΛ ݺͼग़ͤΔΑ͏ʹͳΔɹ-> ΰʔετϝιου
23. Copyright © Kakaku.com Inc. All Rights Reserved. method_missingͷΦʔόʔϥΠυ class Sample def method_missing(name) puts “͋ͳͨ͸ΰʔετϝιου #{name} ϝιουΛݺͼग़͠·ͨ͠” end end sample = Sample.new sample.ghost #=> ͋ͳͨ͸ΰʔετϝιου ghost ϝιουΛݺͼग़͠·ͨ͠
24. method_missingͷࠇຐज़ͬ΀Γ
25. Copyright © Kakaku.com Inc. All Rights Reserved. method_missingͷࠇຐज़ͬ΀Γ • ΰʔετϝιου͸respond_to?Ͱ͸falseͱͳΔ sample = Sample.new sample.ghost #=> ͋ͳͨ͸ΰʔετϝιου ghost ϝιουΛݺͼग़͠·ͨ͠ sample.respond_to?(:ghost) #=> false
26. Copyright © Kakaku.com Inc. All Rights Reserved. method_missingͷࠇຐज़ͬ΀Γ • respond_to?ϝιουͰtrueΛฦ͢Α͏ʹ͢Δʹ͸ respond_to_missing?ϝιουʢObjectΫϥεͷprivateΠϯελϯε ϝιουʣΛΦʔόʔϥΠυ͠Α͏
27. Copyright © Kakaku.com Inc. All Rights Reserved. method_missingͷΦʔόʔϥΠυ class DS def get_keyboard_info(computer_id); end end class Computer def initialize(id, data_source) @id = id @data_source = data_source end def method_missing(name) @data_source.send(“get_#{name}_info, @id end def respond_to_missing?(method, include_private = false) @data_source.respond_to?(“get_#{method}_info”) || super end end
28. Copyright © Kakaku.com Inc. All Rights Reserved. method_missingͷࠇຐज़ͬ΀Γ • ແݶϧʔϓʹೖͬͯ͠·͏Մೳੑ
29. Copyright © Kakaku.com Inc. All Rights Reserved. method_missingͷࠇຐज़ͬ΀Γ • ແݶϧʔϓʹೖͬͯ͠·͏Մೳੑ • super ೖΕΑ͏
30. Copyright © Kakaku.com Inc. All Rights Reserved. method_missingͷࠇຐज़ͬ΀Γ class Roulette def method_missing(name, *args) person = name.to_s.capitalize 3.times do number = rand(10) + 1 puts “#{number}…” end “#{person} got a #{number}” end end
31. Copyright © Kakaku.com Inc. All Rights Reserved. method_missingͷࠇຐज़ͬ΀Γ class Roulette def method_missing(name, *args) person = name.to_s.capitalize 3.times do number = rand(10) + 1 puts “#{number}…” end “#{person} got a #{number}” end end
32. Copyright © Kakaku.com Inc. All Rights Reserved. method_missingͷࠇຐज़ͬ΀Γ class Roulette def method_missing(name, *args) person = name.to_s.capitalize super unless %w[Bob Frank Bill].include? person number = 0 3.times do number = rand(10) + 1 puts “#{number}…” end “#{person} got a #{number}” end end
33. Copyright © Kakaku.com Inc. All Rights Reserved. method_missingͷࠇຐज़ͬ΀Γ • طଘͷϝιουΛݺͼग़͢Մೳੑ • undef ΍ ϒϥϯΫεϨʔτ ͰରԠ
34. Copyright © Kakaku.com Inc. All Rights Reserved. method_missingͷࠇຐज़ͬ΀Γ “ϒϥϯΫεϨʔτ͕ඞཁͰ͋Ε͹ɺBasicObjectΛ௚઀ܧঝ͢Ε͹͍͍ɻ” ʢϝλϓϩάϥϛϯάRuby ୈ2൛ 3ষΑΓʣ
35. Copyright © Kakaku.com Inc. All Rights Reserved. method_missingͷࠇຐज़ͬ΀Γ irb(main):002:0> cmp = Computer.new(@id, DS.new) (Object doesn't support #inspect) =>
36. Copyright © Kakaku.com Inc. All Rights Reserved. method_missingͷࠇຐज़ͬ΀Γ irb(main):002:0> cmp = Computer.new(@id, DS.new) (Object doesn't support #inspect) => irb(main):003:0> cmp.class NoMethodError (undefined method `class' for #<Computer: 0x00007fdc2d0e7a70>)
37. Copyright © Kakaku.com Inc. All Rights Reserved. method_missingͷࠇຐज़ͬ΀Γ “BasicObject͸respond_to?ϝιουΛ͍࣋ͬͯͳ͍ɻ ʢதུʣ respond_to_missing?ϝιου͕ෆཁʹͳΔͷͰɺ࡟আՄೳͩɻ” ʢϝλϓϩάϥϛϯάRuby ୈ2൛ 3ষΑΓʣ
38. Copyright © Kakaku.com Inc. All Rights Reserved. method_missingͷࠇຐज़ͬ΀Γ irb(main):003:0> cmp.respond_to?(:keyboard) NoMethodError (undefined method `respond_to?' for #<Com puter:0x00007fdc2d0e7a70>)
39. ·ͱΊ
40. Copyright © Kakaku.com Inc. All Rights Reserved. method_missingͷΦʔόʔϥΠυ • ఆٛ͞Ε͍ͯͳ͍ϝιουʢΰʔετϝιουʣΛݺͼग़ͤΔΑ͏ʹͳΔ • ΰʔετϝιουʹ͍ͭͯrespond_to?ͰtrueΛฦ͢Α͏ʹ͍ͨ͠ͳΒ respond_to_missing?ϝιουΛΦʔόʔϥΠυ͠Α͏ • super Λ๨Εͣʹ • طଘͷϝιουΛݺͼग़ͯ͠͠·͏ՄೳੑΛ๨Εͣʹ
41. Copyright © Kakaku.com Inc. All Rights Reserved. method_missingͷΦʔόʔϥΠυ • ఆٛ͞Ε͍ͯͳ͍ϝιουʢΰʔετϝιουʣΛݺͼग़ͤΔΑ͏ʹͳΔ • ΰʔετϝιουʹ͍ͭͯrespond_to?ͰtrueΛฦ͢Α͏ʹ͍ͨ͠ͳΒ respond_to_missing?ϝιουΛΦʔόʔϥΠυ͠Α͏ • super Λ๨Εͣʹ • طଘͷϝιουΛݺͼग़ͯ͠͠·͏ՄೳੑΛ๨Εͣʹ
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