プロを目指す人のための例外処理（再）入門 / #rubykansai 2018-01-13

第80回 Ruby関西 勉強会の発表資料です。
https://rubykansai.doorkeeper.jp/events/69011

Transcript

1. ϓϩΛ໨ࢦ͢ਓͷͨΊͷྫ֎ॲཧʢ࠶ʣೖ໳ ҏ౻३Ұ (@jnchito) 2018.01.13 ୈ80ճ Rubyؔ੢ ษڧձ
2. About Me • ҏ౻३Ұ • RailsϓϩάϥϚ@SonicGarden • ϦϞʔτϫʔΧʔ • Ϊλʔ޷͖ • Blog: give IT a try • Twitter: @jnchito
3. ฌݿݝ੢࿬ࢢࡏॅʢग़਎͸େࡕ෎๛தࢢʣ
4. everyday Rails RSpecʹΑΔRails ςετೖ໳ Rails 5.1 + RSpec 3.6ʹ ۙ೔Ξοϓσʔτ༧ఆʂ
5. ϓϩΛ໨ࢦ͢ਓͷ
 ͨΊͷRubyೖ໳ ޷ධൃചதʂʂ
6. ࠓ೔͓࿩͢͠Δ͜ͱ • ྫ֎ͱྫ֎ॲཧʹ͍͓ͭͯ͞Β͍ • ຊ౰ʹ͋ͬͨා͍࿩ • ྫ֎ॲཧͷόουϓϥΫςΟεˍϕετϓϥΫςΟε • ྫ֎ॲཧʢओʹઃܭʣʹؔ͢Δߴ౓ͳτϐοΫ • ۀ຿ΤϥʔͱγεςϜΤϥʔͷҧ͍ • ྫ֎ॲཧͱϩʔϧόοΫͷؔ܎ • ߈Ίͷྫ֎ʢҙਤతʹྫ֎Λൃੜͤ͞Δʣ
7. ྫ֎ͱྫ֎ॲཧʹ͍͓ͭͯ͞Β͍
8. ྫ֎ͱྫ֎ॲཧʹ͍͓ͭͯ͞Β͍ • ྫ֎(Exception)ͱ͸ • ͦΕҎ্ϓϩάϥϜΛଓߦͰ͖ͳ͍ྫ֎తͳঢ়گ • ࡶʹݴ͑͹ϓϩάϥϜͷΤϥʔ • ྫ֎ॲཧͱ͸ • ൃੜͨ͠ྫ֎Λద੾ʹॲཧ͢Δ͜ͱ • ΤϥʔͱແԑͰ͍ΒΕΔϓϩάϥϜ͸ͳ͍ • Αͬͯਖ਼͍͠ྫ֎ॲཧΛֶͿ͜ͱ͸ඇৗʹॏཁ
9. Rubyʹ͓͚Δྫ֎ॲཧͷجຊߏจ begin # Τϥʔ͕ൃੜ͢Δ͔΋͠Εͳ͍ॲཧ a = 1 / 0 rescue => e # Τϥʔ͕ى͖ͨ৔߹ͷॲཧ puts "Τϥʔ͕ൃੜ͠·ͨ͠: #{e.message}” end # ϝιουશମ͕ྫ֎ॲཧͷର৅ʹͳΔ৔߹͸begin/endΛলུͰ͖Δ def some_method 1 / 0 rescue ZeroDivisionError => e puts "ZeroDivisionError͕ൃੜ͠·ͨ͠: #{e.message}" end # ্ͷίʔυͱԼͷίʔυ͸ಉ͡ def some_method begin 1 / 0 rescue ZeroDivisionError => e puts "ZeroDivisionError͕ൃੜ͠·ͨ͠: #{e.message}" end end
10. ͨͩ͠ɺ͜ΕͰऴΘΔͱ΍͹͍ • ʮϋϯϚʔΛ࣋ͭਓʹ͸͢΂͕ͯఝʹݟ͑Δʯ • ྫ֎ॲཧΛ֮͑ͨਓ͸ྫ֎ॲཧΛ࢖͍ͨ͘ͳΔ • Τϥʔ͕ى͖ͨΒrescue͢Ε͹͍͍ͱצҧ͍͢Δ • ͋ͬͪͬͪ͜ʹbegin/rescueΛຒΊࠐΉ • ʮΤϥʔʹڧ͍ϓϩάϥϜ͕Ͱ͖ͨYOʂʘ(^O^)ʗʯ • Ͱ͸͋Γ·ͤΜʂʂ!
11. ຊ౰ʹ͋ͬͨා͍࿩
12. ຊ౰ʹ͋ͬͨා͍࿩ʢલ৬Ͱͷମݧஊʣ • ͱ͋ΔWebγεςϜʢࣾ಺γεςϜʣΛड͚ܧ͍ͩ • ͦͷγεςϜ͸໰୊ͳ͘ಈ͍͍ͯͨʢΑ͏ʹݟ͑ͨʣ • γεςϜվमͷͨΊݱ৔ͷਓͱ࿩͢ػձΛ΋ͬͨ • ݱ৔ͷਓͷ࢖͍ํΛݟͤͯ΋Βͬͨ • อଘϘλϯΛΫϦοΫˠʮγεςϜΤϥʔ: -1ʯ • ๻ʮ͑ͬɺԿ͜Εʁʯ • ݱ৔ͷਓʮ͜Ε͕ग़ͨΒϘλϯΛ࠶ΫϦοΫ͠·͢ʯ
13. Πϝʔδతʹ͸͜͏ʢ࣮ࡍ͸ASP.NETʣ • Τϥʔ͕ൃੜͨ͠ΒΤϥʔίʔυΛදࣔͯ͠ऴΘΓ • ௨஌΋͞Εͳ͍ɺϩάʹ΋·ͬͨ͘৘ใ͕࢒Βͳ͍ • ݱ৔͸ʮΤϥʔ͕ग़ͨΒ࠶ΫϦοΫʯΛϚχϡΞϧԽ • ͦͷޙͷௐࠪˠઃܭϛεͰσουϩοΫ͕සൃͯͨ͠ def create @post = Post.new(post_params) @post.save! redirect_to post_path(@post) rescue => e flash.now[:alert] = "γεςϜΤϥʔ: #{e.error_code}" render action: :new end
14. ଞʹ΋͜Μͳͷͱ͔ʢ࣮ࡍ͸C#ʣ class PostService def find_data(id) # औಘͨ͠σʔλ͸ͳ͔ͥΠϯελϯεม਺ʹηοτ͞ΕΔ @data = Post.find(id) # ੒ޭ·ͨ͸ࣦഊΛ਺஋Ͱฦ͢ return 1 rescue => e # Τϥʔ͕ى͖ͨΒϝοηʔδ͚ͩ֨ೲͯ͠0Λฦ͢ @error_message = e.message return 0 end def save_data(data) # ΄͔ͷϝιου΋ಉ͡Α͏ͳྫ֎ॲཧ͕ॻ͔Ε͍ͯΔ end end # ҰԠ໭Γ஋͸ड͚औΔ͕ɺ1͔0ͷνΣοΫ͸͠ͳ͍ ret = post_service.find_data(id) # Կ΋ߟ͑ͣʹσʔλΛऔͬͯ͘Δ post = post_service.data # औಘʹࣦഊͨ͠Βpost͸nilͳͷͰɺ͜͜ͰΤϥʔ͕ى͖Δ title = post.title ☠
15. ͜ͷ݅ͷڭ܇ͱྫ֎ॲཧͷجຊతͳߟ͑ํ • ྫ֎ॲཧ͸࢖͍ํΛؒҧ͑Δͱɺ֐ͷํ͕େ͖͘ͳΔ • Ͱ͖Δ͜ͱͱɺ΍͍͍ͬͯ͜ͱ͸ҟͳΔ • ྫ֎ॲཧͷجຊతͳߟ͑ํ • ૉਓ͸rescue͢Μͳʂʂ • Τϥʔ͕ग़ͨΒͦ͜ͰʓͶʂʂ • ྫ֎ॲཧ͸ϑϨʔϜϫʔΫͷڞ௨ॲཧʹ·͔ͤΖʂʂ
16. ྫ֎ॲཧΛ࢖ͬͯ΋ڐ͞ΕΔέʔεɾͦͷ1 • ଞͷ஥ؒΛಓͮΕʹͨ͘͠ͳ͍৔߹ # ෳ਺ͷϢʔβʔʹҰׅͰϝʔϧΛૹ৴͢Δ users.each do |user| begin # ଞͷϢʔβʔΛಓͮΕʹ͠ͳ͍Α͏ɺΤϥʔ͕ى͖ͯ΋ଓߦ͢Δ send_mail_to(user) rescue => e puts "#{e.class}: #{e.message}" puts e.backtrace end end
17. ྫ֎ॲཧΛ࢖ͬͯ΋ڐ͞ΕΔέʔεɾͦͷ2 • ྫ֎ͷ༗ແͰ͔͠ཁ݅Λຬͨͤͳ͍৔߹ require 'json' def valid_json_format?(text) # ࣮ࡍʹύʔεͯ͠Τϥʔ͕ൃੜ͢Δ͔Ͳ͏͔νΣοΫ͢Δ͔͠ͳ͍ JSON.parse(text) true rescue JSON::ParserError false end valid_json_format?('{ "a": 1 }') #=> true valid_json_format?('{ "a": 1') #=> false
18. ྫ֎ॲཧͷόουϓϥΫςΟε☠
19. 1. ྫ֎ͷѲΓͭͿ͠☠ • ୭΋Τϥʔʹؾ͔ͮͳ͍ɺ͋ͱͰௐࠪ΋Ͱ͖ͳ͍ • ্ͷྫ͸ۃ୺͕ͩɺ݁Ռతʹແࢹ͞ΕΔ৔߹΋͋Δ • ໭Γ஋͕ແࢹ͞Εͨ৔߹ͳͲ user = build_user(data) # ൃੜͨ͠Τϥʔ͸׬શʹແࢹ͞ΕΔ begin save(user) rescue end # Կࣄ΋ͳ͔͔ͬͨͷΑ͏ʹॲཧΛଓߦ send_mail_to(user)
20. 2. ExceptionΫϥεΛrescue͍ͯ͠Δ☠ • StandardErrorҎԼΛัଊ͢Δͷ͕ਖ਼ղ begin save(user) rescue Exception => e # ԿΒ͔ͷΤϥʔॲཧ end ϓϩΛ໨ࢦ͢ਓͷͨΊͷRubyೖ໳
 ୈ9ষʹొ৔͢Δਤ
21. ࢀߟ # ໌ࣔతʹStandardErrorΛࢦఆ͢Δ begin save(user) rescue StandardError => e # ԿΒ͔ͷΤϥʔॲཧ end # ྫ֎ΫϥεΛࢦఆ͠ͳ͚Ε͹StandardErrorͱͦͷαϒΫϥε͕rescue͞ΕΔ begin save(user) rescue => e # ԿΒ͔ͷΤϥʔॲཧ end • ্ͷ2ͭ͸΍͍ͬͯΔ͜ͱ͸ಉ͡ • ͳͷͰɺԼͷΑ͏ʹStandardError͸লུ͢Ε͹ྑ͍
22. 3-1. begin͔Βrescue·Ͱͷൣғ͕ແବʹ޿͍☠ • Ͳ͜Ͱൃੜ͢ΔΤϥʔΛัଊ͍ͨ͠ͷ͔Θ͔Βͳ͍ # ฏ੒ͷ೔෇จࣈྻΛDateΦϒδΣΫτʹม׵͢Δ def convert_heisei_to_date(heisei_text) begin m = heisei_text.match(/ฏ੒(?<jp_year>\d+)೥(?<month>\d+)݄(?<day>\d+)೔/) year = m[:jp_year].to_i + 1988 month = m[:month].to_i day = m[:day].to_i Date.new(year, month, day) rescue # ྫ֎͕ى͖ͨΒʢʹແޮͳ೔෇͕౉͞ΕͨΒʣnilΛฦ͍ͨ͠ nil end end } {
23. 3-2. rescueઅʹྫ֎ΫϥεΛԿ΋ࢦఆ͠ͳ͍☠ • λΠϓϛε͕ݪҼͰൃੜͨ͠ྫ֎΋ัଊ͞Εͯ͠·͏ # ฏ੒ͷ೔෇จࣈྻΛDateΦϒδΣΫτʹม׵͢Δ def convert_heisei_to_date(heisei_text) begin m = heisei_text.match(/ฏ੒(?<jp_year>\d+)೥(?<month>\d+)݄(?<day>\d+)೔/) year = m[:jp_year].to_i + 1988 month = m[:month].to_i day = m[:day].to_i Date.new(year, month, day) rescue # ྫ֎͕ى͖ͨΒʢʹແޮͳ೔෇͕౉͞ΕͨΒʣnilΛฦ͍ͨ͠ nil end end
24. 4. ྫ֎ॲཧΛςετ͠ͳ͍☠ • ؊৺ͷຊ൪؀ڥͰॳΊͯྫ֎ॲཧͷόάʹؾͮ͘ • ΋ͱ΋ͱൃੜ͍ͯͨ͠ΤϥʔͷݪҼ͕ࣦΘΕͯ͠·͏ • લ৬Ͱܦݧ͋ΓʢҾ͖ܧ͍ͩγεςϜͰɾɾɾʣ def some_method 1 / 0 rescue => e # messageͱॻͭ͘΋Γ͕mesageͱॻ͍ͯ͠·ͬͨ puts "Τϥʔ͕ൃੜ͠·ͨ͠: #{e.mesage}" puts e.backtrace end
25. ωοτͷهࣄʹ͸ཁ஫ҙ • όουϓϥΫςΟεΛ঺հ͍ͯ͠Δهࣄ΋ଟ͍ • ͦΜͳهࣄͰ΋άάͬͨͱ͖ʹ্Ґʹग़͖ͯͯ͠·͏ • ExceptionΛrescueͯ͠Δهࣄͱ͔ɺΑ͘ݟ͔͚Δ • ͦΜͳهࣄΛӏವΈʹ͠ͳ͍Α͏ʹʂ
26. ྫ֎ॲཧͷϕετϓϥΫςΟε
27. 1. ݪଇͱͯ͠rescue͠ͳ͍ • ྫ֎ॲཧͷجຊతͳߟ͑ํʢ࠶ܝʣ • ૉਓ͸rescue͢Μͳʂʂ • Τϥʔ͕ग़ͨΒͦ͜ͰʓͶʂʂ • ྫ֎ॲཧ͸ϑϨʔϜϫʔΫͷڞ௨ॲཧʹ·͔ͤΖʂʂ • Ҏ߱͸rescue͕Ͳ͏ͯ͠΋ඞཁͳঢ়گΛ૝ఆ
28. 2. ྫ֎ͷ৘ใΛϩάʹ࢒͢ˍ௨஌͢Δ • ྫ֎Ϋϥε໊ɺϝοηʔδɺόοΫτϨʔεΛϩάग़ྗ • Bugsnag΍RollbarɺErrbitͳͲͰ։ൃऀʹ௨஌͢Δ • Τϥʔʹ͙͢ؾ͖ͮɺ͙͢ௐࠪͰ͖ΔΑ͏ʹ͢Δ begin save(user) rescue => e # ϩάʹ࢒͢ logger.error "#{e.class} / #{e.message}" logger.error e.backtrace.join("\n") # ௨஌͢Δ Bugsnag.notify(e) end
29. 3. ྫ֎ॲཧͷର৅ൣғͱର৅ΫϥεΛߜΓࠐΉ • ัଊ͍ͨ͠Τϥʔ͚ͩΛ࣮֬ʹૂ͍ܸͪ͢Δ • ͦΕҎ֎ͷΤϥʔ͕ग़ͨΒଈɺҟৗऴྃͤ͞Δ def convert_heisei_to_date(heisei_text) m = heisei_text.match(/ฏ੒(?<jp_year>\d+)೥(?<month>\d+)݄(?<day>\d+)೔/) year = m[:jp_year].to_i + 1988 month = m[:month].to_i day = m[:day].to_i # ྫ֎ॲཧͷൣғΛڱΊɺัଊ͢Δྫ֎ΫϥεΛݶఆ͢Δ begin Date.new(year, month, day) rescue ArgumentError # ແޮͳ೔෇Ͱ͋Ε͹nilΛฦ͢ nil end end
30. ࢀߟ • ྫ֎ॲཧΛ࢖ΘͣʹࡁΉํ๏͕͋Ε͹ͦΕΛ࢖͏΂͖ def convert_heisei_to_date(heisei_text) m = heisei_text.match(/ฏ੒(?<jp_year>\d+)೥(?<month>\d+)݄(?<day>\d+)೔/) year = m[:jp_year].to_i + 1988 month = m[:month].to_i day = m[:day].to_i # ྫ֎ॲཧͰ͸ͳ͘ɺ৚݅෼ذΛ࢖͏ if Date.valid_date?(year, month, day) Date.new(year, month, day) end end
31. 4. ྫ֎ॲཧ΋ςετ͢Δ • ྫ֎ॲཧͷڍಈΛ֬ೝͰ͖ΔςετίʔυΛॻ͘ • ࠶ݱ͕೉͍͠৔߹͸ϞοΫΛ׆༻͢Δ def some_method 1 / 0 rescue => e puts "Τϥʔ͕ൃੜ͠·ͨ͠: #{e.message}" puts e.backtrace end class SampleTest < Minitest::Test def test_some_method assert_output /Τϥʔ͕ൃੜ͠·ͨ͠/ do some_method end end end
32. ྫ֎ॲཧʢओʹઃܭʣʹؔ͢Δߴ౓ͳτϐοΫ
33. 1. ۀ຿ΤϥʔͱγεςϜΤϥʔͷҧ͍
34. Τϥʔʹ͸2छྨͷΤϥʔ͕͋Δ • ۀ຿ΤϥʔʢϏδωεྫ֎ʣ • ೖྗϑΥʔϜʹ͓͚ΔϢʔβʔͷೖྗϛε • ݖݶҧ൓ʢݖݶͷͳ͍ϖʔδ΁ͷΞΫηε౳ʣ • γεςϜΤϥʔʢٕज़తྫ֎ʣ • ϓϩάϥϜͷϛεʢ͍ΘΏΔόάʣ • ωοτϫʔΫΤϥʔɺσʔλϕʔεͷμ΢ϯ౳ • ։ൃऀ͸͜ͷ۠ผΛ෇͚ͳͯ͘͸ͳΒͳ͍
35. ۀ຿Τϥʔ΁ͷରॲʢը໘ઃܭʣ • Ϣʔβʔʹ΍Γ௚ͤ͠͞Δʢ͓લ͕ѱ͍ͱ఻͑Δʣ
36. ۀ຿Τϥʔ΁ͷରॲʢ಺෦ઃܭɾͦͷ1ʣ • ྫ֎ॲཧ͸ݪଇͱͯ͠࢖Θͳ͍ • ੒ޭ or ࣦഊ͸ϝιουͷ໭Γ஋Ͱදݱ͢Δ • ݺͼग़͠ଆ͸ඞͣ໭Γ஋Λݕূ͢Δ def create @event = Event.new(event_params) # saveϝιουͷ໭Γ஋ΛνΣοΫ if @event.save # ໭Γ஋͕trueͳͷͰ੒ޭ redirect_to @event, notice: 'Event was successfully created.' else # ໭Γ஋͕falseͳͷͰࣦഊ render :new end end
37. ۀ຿Τϥʔ΁ͷରॲʢ಺෦ઃܭɾͦͷ2ʣ • ෆඞཁʹྫ֎ॲཧΛ࢖Θͳ͍͜ͱ • ྫ֎ॲཧΛͳͯ͘͠΋ۀ຿ΤϥʔʹରॲͰ͖Δ͔ʁ • NOͳΒॲཧϑϩʔͷ੍ޚʹྫ֎ॲཧΛ࢖͍ͬͯΔ # ϓϩδΣΫτͷશؔ܎ऀʹରͯ͠కΊ੾ΓͷมߋΛࢼΈΔϝιου def extend_deadline_for_all_stakeholders(project, new_deadline) project.developers.each do |developer| developer.update!(deadline: new_deadline) end project.customer.update!(deadline: new_deadline) project.manager.update!(deadline: new_deadline) true rescue ActiveRecord::RecordInvalid # ۀ຿Τϥʔͳͷʹྫ֎ॲཧΛ࢖͍ͬͯΔʢNGʣ false end
38. ࢀߟ • ྫ֎ॲཧΛ࢖Θͣʹ࣮૷͢Δ৔߹ͷίʔυྫ def extend_deadline_for_all_stakeholders(project, new_deadline) all_success = true project.developers.each do |developer| all_success &= developer.update(deadline: new_deadline) end all_success &= project.customer.update(deadline: new_deadline) all_success &= project.manager.update(deadline: new_deadline) # ্ͷॲཧͰ1ͭͰ΋false͕ฦΕ͹ɺall_success͸falseʹมΘΔ # ʢຊདྷ͸σʔλϕʔετϥϯβΫγϣϯͷϩʔϧόοΫ΋ߟྀ͢΂͖ɻৄࡉ͸ޙड़ʣ all_success end
39. γεςϜΤϥʔ΁ͷରॲʢը໘ઃܭʣ • ͝ΊΜɺͬͪ͜Ͱରॲ͢Δ͔Β଴ͬͯͯɺͱ఻͑Δ • ͍ΘΏΔ500Τϥʔը໘Λදࣔ͢Δ
40. γεςϜΤϥʔ΁ͷରॲʢ಺෦ઃܭʣ • ݪଇ͸Կ΋͠ͳ͍ • ଈ࠲ʹۓٸఀࢭͤ͞ɺڞ௨ॲཧʹ·͔ͤΔ • ΍ΉΛಘͳ͍৔߹ͷΈɺrescueͯ͠ଓߦ͢Δ • ΋ͪΖΜϩάग़ྗ΍௨஌͸ඞਢʂ
41. 2. ྫ֎ॲཧͱϩʔϧόοΫͷؔ܎
42. ྫ֎ॲཧͱϩʔϧόοΫͷؔ܎ • ʮΞτϛοΫૢ࡞͸Կ͔ʯΛৗʹҙࣝ͢Δ • ΞτϛοΫૢ࡞ʢෆՄ෼ૢ࡞ʣͱ͸ • શͯͷมߋ͕੒ޭͨ͠ͱ͖ͷΈɺมߋΛ֬ఆ • 1ͭͰ΋ࣦഊ͢Ε͹શ෦ΩϟϯηϧʢϩʔϧόοΫʣ • ྫ • ෳ਺ͷϨίʔυΛಉ࣌ʹߋ৽͢Δ৔߹ • σʔλϕʔεߋ৽ޙʹ՝ܾۚࡁAPIΛݺͼग़͢৔߹
43. RailsͰෳ਺ͷϨίʔυΛಉ࣌ʹߋ৽͢Δ৔߹ • transactionϝιουͱRollbackྫ֎Λ׆༻͢Δ • γεςϜΤϥʔ͕ى͖ͨΒͦ͜ͰϩʔϧόοΫ • ۀ຿ΤϥʔͳΒRollbackྫ֎Ͱ໌ࣔతʹϩʔϧόοΫ def extend_deadline_for_all_stakeholders(project, new_deadline) all_success = true transaction do project.developers.each do |developer| all_success &= developer.update(deadline: new_deadline) end all_success &= project.customer.update(deadline: new_deadline) all_success &= project.manager.update(deadline: new_deadline) unless all_success # ໌ࣔతʹϩʔϧόοΫͤ͞Δʢtransactionϝιου͕rescue͢ΔͷͰॲཧ͸ଓߦ͞ΕΔʣ raise ActiveRecord::Rollback end end all_success end ] [
44. 3. ߈Ίͷྫ֎ʢҙਤతʹྫ֎Λൃੜͤ͞Δʣ
45. ߈Ίͷྫ֎ ͦͷ1: ༧ظͤ͵৚݅෼ذΛ͢ • ༧ظͤ͵৚݅෼ذʹೖͬͨΒྫ֎Λൃੜͤ͞Δ • ࢮ͵͸ͣͷϓϩάϥϜΛແཧʹੜ͔ͯ͠͸͍͚ͳ͍ # elseʹೖͬͨΒྫ֎Λൃੜͤ͞Δύλʔϯʢྑ͍ྫʣ def currency_of(country) case country when :japan 'yen' when :us 'dollar' when :india 'rupee' else raise ArgumentError, "ແޮͳࠃ໊Ͱ͢ɻ#{country}" end end # ྫ֎͕ൃੜ͢Δ currency_of(:italy) #=> ArgumentError: ແޮͳࠃ໊Ͱ͢ɻitaly
46. ࢀߟ: ࢮ͵͸ͣͳͷʹɺࢮͳͳ͍έʔεɾͦͷ1 • else͕ͳ͍ → nil͕ฦͬͯ͠·͏ # elseΛ༻ҙ͠ͳ͍ύλʔϯʢྑ͘ͳ͍ྫʣ def currency_of(country) case country when :japan 'yen' when :us 'dollar' when :india 'rupee' end end # ૝ఆ֎ͷࠃ໊Λ౉͢ͱnil͕ฦΔ currency = currency_of(:italy) #=> nil # ༧ظͤ͵λΠϛϯάͰΤϥʔ͕ൃੜ͢Δ currency.upcase #=> NoMethodError: undefined method `upcase' for nil:NilClass
47. ࢀߟ: ࢮ͵͸ͣͳͷʹɺࢮͳͳ͍έʔεɾͦͷ2 • elseͰಛఆͷ஋Λฦ͢ → ໃ६ͨ͠஋͕ฦͬͯ͠·͏ # elseΛ:indiaͱͯ͠ѻ͏ύλʔϯʢྑ͘ͳ͍ྫʣ def currency_of(country) case country when :japan 'yen' when :us 'dollar' else 'rupee' end end # ໃ६ͨ͠஋͕ฦ͖ͬͯͯ͠·͏ country = :italy currency = currency_of(country) #=> “rupee” price = 100 "#{country}: #{price}#{currency}" #=> "italy: 100rupee"
48. ߈Ίͷྫ֎ ͦͷ2: ͋Γಘͳ͍Τϥʔʹ͸ڧؾͰ • ۀ຿Τϥʔ͢ΒγεςϜΤϥʔͱݟͳͤΔ৔߹΋͋Δ • ͦ͏͍͏έʔεͰ͸save!΍update!Λ࢖͏ • ͨͩ͠ɺΞτϛοΫૢ࡞͚ͩ͸ҡ࣋͢ΔΑ͏ʹ def extend_deadline_for_all_stakeholders(project, new_deadline) # ສҰͷࣄଶʹ͸උ͓͑ͯ͘ʢσʔλϕʔε΁ͷมߋΛΞτϛοΫૢ࡞ʹ͢Δʣ transaction do # ୭Ұਓͱͯ͠కΊ੾ΓͷԆ௕ʹ͸จ۟ΛݴΘͳ͍͸ͣͩʂʢจ۟ΛݴΘΕͨΒγεςϜΤϥʔʣ project.developers.each do |developer| developer.update!(deadline: new_deadline) end project.customer.update!(deadline: new_deadline) project.manager.update!(deadline: new_deadline) end end
49. ·ͱΊ
50. ·ͱΊ: ਖ਼͍͠ྫ֎ॲཧͰ޾ͤͳਓੜΛ̇ • ྫ֎ͱྫ֎ॲཧʹ͍͓ͭͯ͞Β͍ • ຊ౰ʹ͋ͬͨා͍࿩ • ྫ֎ॲཧͷόουϓϥΫςΟεˍϕετϓϥΫςΟε • ྫ֎ॲཧʢओʹઃܭʣʹؔ͢Δߴ౓ͳτϐοΫ • ۀ຿ΤϥʔͱγεςϜΤϥʔͷҧ͍ • ྫ֎ॲཧͱϩʔϧόοΫͷؔ܎ • ߈Ίͷྫ֎ʢҙਤతʹྫ֎Λൃੜͤ͞Δʣ
51. ࢀߟจݙ • .NETͷྫ֎ॲཧ Part.1ʢ@nakama00ɺ2008೥ʣ • ྫ֎ઃܭʹ͓͚Δେࡑʢ@t_wadaɺ2012೥ʣ • RailsΞϓϦέʔγϣϯʹ͓͚ΔΤϥʔॲཧʢྫ֎ઃܭʣͷߟ͑ํʢ@jnchitoʣ • give IT a tryʢ@jnchitoʣ • Nasty design can blast your brain!ʢ2010೥3݄31೔ʣ • ٕज़ॻ௥Ճͦͷ2ʢ2010೥4݄10೔ʣ • and…
52. ϓϩΛ໨ࢦ͢ਓͷ
 ͨΊͷRubyೖ໳ ୈ9ষ ྫ֎ॲཧΛཧղ͢Δ
53. @jnchito blog.jnito.com 'PMMPX
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