読みやすいコードの書き方 第 1 回 / Code readability: Session 1 (ver. 2, Ja)

第 1 回: 導入と原則

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セッションリスト

第 1 回: 導入と原則
- https://speakerdeck.com/munetoshi/code-readability-session-1-ver-2-ja

第 2 回: 命名
- https://speakerdeck.com/munetoshi/code-readability-session-2-ver-2-ja

第 3 回: コメント
- https://speakerdeck.com/munetoshi/code-readability-session-3-ver-2-ja

第 4 回: 状態
- https://speakerdeck.com/munetoshi/code-readability-session-4-ver-2-ja

第 5 回: 関数
- https://speakerdeck.com/munetoshi/code-readability-session-5-ver-2-ja

第 6 回: 依存関係 I
- https://speakerdeck.com/munetoshi/code-readability-session-6-ver-2-ja

第 7 回: 依存関係 II
- https://speakerdeck.com/munetoshi/code-readability-session-7-ver-2-ja

第 8 回: レビュー
- https://speakerdeck.com/munetoshi/code-readability-session-8-ver-2-ja

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関連書籍 「読みやすいコードのガイドライン - 持続可能なソフトウェア開発のために」
- https://gihyo.jp/book/2022/978-4-297-13036-7

英語版のリスト: https://gist.github.com/munetoshi/65a1b563fb2c271f328c121a4ac63571#file-code-readability-links-md

以前のバージョン (英語): https://speakerdeck.com/munetoshi/code-readability

© 2019-2023 Munetoshi Ishikawa, supported by LINE corporation

Transcript

1. ಡΈ΍͍͢ίʔυͷॻ͖ํ
2. ॻ੶ʹ͍ͭͯ ಡΈ΍͍͢ίʔυͷΨΠυϥΠϯ - ࣋ଓՄೳͳιϑτ΢ΣΞ։ൃͷͨΊʹ - 2022೥10݄22೔ग़൛, ٕज़ධ࿦ࣾ https://gihyo.jp/book/ 2022/978-4-297-13036-7
3. ಡΈ΍͍͢ίʔυͷॻ͖ํ ୈ 1 ճ ಋೖͱݪଇ
4. ಡΈ΍͍͢ίʔυͷཁ݅ - ໌֬: flag ΑΓ isVisible - ୯७: !(!isA || !isB) && isB ΑΓ isA && isB - ಠཱੑ͕ߴ͍: ؔ਺, Ϋϥε, Ϟδϡʔϧ... - ߏ଄త: ϑΥʔϚοτ, ґଘؔ܎, ঢ়ଶભҠ... ҰͭͷࢦඪͰ͸ಡΈ΍͢͞ΛଌΕͳ͍ ʮԿ͕ಡΈ΍͍͔͢ʯ͸࣌୅ͱίϯςΩετʹґଘ͢Δ ಋೖͱݪଇ > ಋೖ
5. ಡΈ΍͢͞ͷඞཁੑ ϓϩμΫτͷن໛͕େ͖͘ͳͬͯ΋ ੜ࢈ੑΛҡ࣋͢ΔͨΊ ಋೖͱݪଇ > ಋೖ
6. ϓϩμΫτͷن໛ͱੜ࢈ੑ ։ൃن໛͕େ͖͘ͳΔ → ੜ࢈ੑ্͕͕Γʹ͍͘ ಡΈ΍͢͞: ։ൃΛܧଓ͠΍͘͢͢Δखஈ ಋೖͱݪଇ > ಋೖ
7. ϓϩμΫτͷن໛ͱίʔυͷಡΈ΍͢͞ ن໛͕େ͖͘ͳΔ΄Ͳ ಡΉ࣌ؒ > ॻ࣌ؒ͘ - ػೳ࣮૷࣌ͷطଘίʔυͷཧղ - ؔ࿈։ൃऀʹίʔυϨϏϡʔґཔ - ෳࡶͳόάͷ 1 ߦमਖ਼ ॻ͖΍͢͞ΑΓಡΈ΍͕͢͞ॏཁ ಋೖͱݪଇ > ಋೖ
8. ੜ࢈ੑͷ࠷దԽ νʔϜશମ ˍ ϓϩμΫτण໋શظؒ ͷੜ࢈ੑ͕ॏཁ 5 ෼ͷվળͰଞͷਓͷ 1 ࣌ؒΛٹ͑Δ͔΋ ίϝϯτ΍ςετͷ௥Ճɾͪΐͬͱͨ͠ϦϑΝΫλϦϯά ։ൃऀͷධՁج४ͷมߋ͕ඞཁ͔΋ ୹ظؒͷ࣮૷଎౓ͷΈʹয఺Λͯͯ͸͍͚ͳ͍ ಋೖͱݪଇ > ಋೖ
9. νʔϜͷੜ࢈ੑͱनਓͷδϨϯϚ ݸਓͷੜ࢈ੑ Ͱ࠷దԽ͢Δͱ νʔϜͷੜ࢈ੑ ͸Լ͕ΓಘΔ Bob Alice Hacky Readable Readable Hacky 8 8 10 1 1 10 2 2 ಋೖͱݪଇ > ಋೖ
10. ՄಡੑΛߴΊΔऔΓ૊Έํ - ஌ࣝ΍ٕज़Λબ୒͢Δ ʢ࢖͏໨తΛݟࣦΘͳ͍ʣ - Ձ஋ͱෳࡶ͞ͷόϥϯε ΛऔΔ - ࣗಈతͳݕূ Λ׆༻͢Δ ʢίϯύΠϥ, ςετ, etc.ʣ - ٞ࿦Λසൟʹߦ͏ ʢϛεͷख໭ΓΛখ͘͢͞Δʣ - ܧଓֶͯ͠श͢Δ ಋೖͱݪଇ > ಋೖ
11. ίʔυͷॻ͖ํͷֶश ࣮૷͢Δ͚ͩͳΒൺֱత؆୯ ಛผͳτϨʔχϯά͸ෆཁ ಡΈ΍͍͢ίʔυΛॻ͘͜ͱ͸೉͍͠ - ߨٛɾॻ੶ɾΦϯϥΠϯࢿྉ - ίʔυϨϏϡʔɾϖΞϓϩάϥϛϯά ಋೖͱݪଇ > ಋೖ
12. ߨٛͷߏ੒ - ಋೖͱݪଇ - ࣗવݴޠ: ໋໊, ίϝϯτ - ܕͷߏ଄: ঢ়ଶ, ؔ਺ - ܕؒͷߏ଄: ґଘؔ܎I, ґଘؔ܎II - ϨϏϡʔ ಋೖͱݪଇ > ಋೖ
13. ߨٛͷߏ੒ - ಋೖͱݪଇ - ࣗવݴޠ: ໋໊, ίϝϯτ - ܕͷߏ଄: ঢ়ଶ, ؔ਺ - ܕؒͷߏ଄: ґଘؔ܎I, ґଘؔ܎II - ϨϏϡʔ ಋೖͱݪଇ > ಋೖ
14. ࠓճͷ಺༰ - ಋೖ - ϘʔΠεΧ΢τϧʔϧ - YAGNIɹ - KISSɹ - ୯Ұ੹೚ݪଇ - ࣌ظঘૣͳ࠷దԽ͸ॾѱͷࠜݯ ಋೖͱݪଇ > ݪଇ
15. ࠓճͷ಺༰ - ಋೖ - ϘʔΠεΧ΢τϧʔϧ - YAGNIɹ - KISSɹ - ୯Ұ੹೚ݪଇ - ࣌ظঘૣͳ࠷దԽ͸ॾѱͷࠜݯ ಋೖͱݪଇ > ݪଇ
16. ϘʔΠεΧ΢τϧʔϧ Try to leave this world a little better than you found it... — Robert Baden-Powell Robert C. Martin ͕ιϑτ΢ΣΞ։ൃʹద༻1 ίʔυʹมߋΛՃ͑Δͱ͖ɺվળΛࢪ͢ 1 97 Things Every Programmer Should Know: Collective Wisdom from the Experts, Kevlin Henney, 2010 ಋೖͱݪଇ > ݪଇ > ϘʔΠεΧ΢τϧʔϧ
17. ϘʔΠεΧ΢τϧʔϧͰ͢΂͖͜ͱ 1/2 - ௥Ճ: ίϝϯτ, ςετ - ࡟আ: ෆཁͳґଘؔ܎, ϝϯό, ঢ়ଶ - ໊લͷมߋ: Ϋϥε, ؔ਺, ม਺ - ෼ׂ: ڊେͳΫϥε, ؔ਺, ωετ, ݺͼग़ؔ͠܎ - ߏ଄Խ: ϑΥʔϚοτ, ґଘؔ܎, ந৅ԽϨΠϠ, ܧঝ֊૚ ಋೖͱݪଇ > ݪଇ > ϘʔΠεΧ΢τϧʔϧ
18. ϘʔΠεΧ΢τϧʔϧͰ͢΂͖͜ͱ 2/2 ίʔυΛѱԽͤ͞ͳ͍ (ׂΕ૭ཧ࿦) ྫ: ڊେͳߏ଄ʹཁૉΛ௥Ճ͢΂͖Ͱͳ͍ - ڊେͳΫϥεɾؔ਺ʹ ϝϯόɾจ Λ௥Ճ͠ͳ͍ - ਂ͍ݺͼग़͠ߏ଄ɾܧঝؔ܎ʹ ֊૚ Λ௥Ճ͠ͳ͍ ಋೖͱݪଇ > ݪଇ > ϘʔΠεΧ΢τϧʔϧ
19. ϘʔΠεΧ΢τϧʔϧͷద༻ྫ 1/3 ໰୊: ৽͍͠ ViewType ͱͯ͠ Z Λ௥Ճͯ͠Α͍ʁ val viewType: ViewType = ... // An enum type when (viewType) { A -> { view1.isVisible = true view2.text = "Case A" } B -> { view1.isVisible = false view2.text = "Case B" } ... ಋೖͱݪଇ > ݪଇ > ϘʔΠεΧ΢τϧʔϧ
20. ϘʔΠεΧ΢τϧʔϧͷద༻ྫ 2/3 ղ౴: ʮͦͷ··Ͱ͸ʯ௥Ճͯ͠͸͍͚ͳ͍ ͢Ͱʹ৚݅෼ذͷߏ଄͕ංେԽ͍ͯ͠ΔͨΊ ղܾҊ: ஋ΛྻڍܕͷϓϩύςΟͱͯ͠நग़ ಋೖͱݪଇ > ݪଇ > ϘʔΠεΧ΢τϧʔϧ
21. ϘʔΠεΧ΢τϧʔϧͷద༻ྫ 3/3 1: ϓϩύςΟͱͯ͠ நग़͢Δ enum class ViewType(val isView1Visible: Boolean, val view2Text: String) 2: ϓϩύςΟΛ࢖ͬͯ ৚݅෼ذΛ࡟আ͢Δ view1.isVisible = viewType.isView1Visible view2.text = viewType.view2Text 3: ৽͍͠λΠϓ Z Λ௥Ճ͢Δ ಋೖͱݪଇ > ݪଇ > ϘʔΠεΧ΢τϧʔϧ
22. ϘʔΠεΧ΢τϧʔϧͷ஫ҙ఺ ϓϧϦΫΤετ΍ίϛοτΛංେԽͤ͞ͳ͍ - ࣮૷ͷʮલʹʯϦϑΝΫλϦϯά ӨڹൣғΛߟ͑Δ - ϦϑΝΫλϦϯάൣғΛ͋Β͔͡ΊܾΊ͓ͯ͘ - ϦϦʔεϒϥϯνͰ͸ϦϑΝΫλϦϯά͠ͳ͍ ಋೖͱݪଇ > ݪଇ > ϘʔΠεΧ΢τϧʔϧ
23. ࠓճͷ಺༰ - ಋೖ - ϘʔΠεΧ΢τϧʔϧ - YAGNIɹ - KISSɹ - ୯Ұ੹೚ݪଇ - ࣌ظঘૣͳ࠷దԽ͸ॾѱͷࠜݯ ಋೖͱݪଇ > ݪଇ
24. YAGNI You Aren't Gonna Need It ඞཁͳͱ͖͚࣮ͩ૷͢Δ - ʮকདྷͷͨΊʯͷػೳͷ 90% ͸࢖ΘΕͳ͍ 2 - ߏ଄Λ୯७ʹอͭ = ࢓༷มߋʹରԠ͠΍͍͢ 2 2 http://www.extremeprogramming.org/rules/early.html ಋೖͱݪଇ > ݪଇ > YAGNI
25. YAGNI ʹҧ൓͍ͯ͠Δίʔυ ࢖ΘΕ͍ͯͳ͍ίʔυ - ࢀর͞Ε͍ͯͳ͍Ϋϥεɾؔ਺ɾม਺ - ίϝϯτΞ΢τ͞Εͨίʔυ ա౓ʹ֦ு͞Εͨίʔυ - ࢠΫϥε͕͚̍ͭͩͷந৅Ϋϥε - ఆ਺͔͠౉͞Εͳ͍Ҿ਺ ಋೖͱݪଇ > ݪଇ > YAGNI
26. YAGNI ʹҧ൓͍ͯ͠Δྫ UI ཁૉͷ࠲ඪΫϥεʹʮ୯ҐʯΛ௥Ճ͢Δ class Coordinate(val x: Int, val y: Int, val unitType: UnitType) enum class UnitType { PIXEL, POINT } Coordinate + Coordinate Λఆٛ͠Α͏ͱ͢Δͱෳࡶʹ ࢖ΘΕ͍ͯͳ͍ػೳͷ࣮૷͸ؒҧͬͨઃܭΛҾ͖ى͜͠΍͍͢ ಋೖͱݪଇ > ݪଇ > YAGNI
27. YAGNI ͷ஫ҙ఺ ػೳͷ࣮૷͕য఺ - ઃܭ΍ػೳͷཁ൱ͷٞ࿦͸ԣணͯ͠͸͍͚ͳ͍ ίʔυͷมߋՄೳੑ͕લఏ - ֎෦ެ։͢Δ APIɾϥΠϒϥϦ౳͸ཁݕ౼ - όʔδϣϯʹΑΔߋ৽खஈ͕ඞཁ ಋೖͱݪଇ > ݪଇ > YAGNI
28. ࠓճͷ಺༰ - ಋೖ - ϘʔΠεΧ΢τϧʔϧ - YAGNIɹ - KISSɹ - ୯Ұ੹೚ݪଇ - ࣌ظঘૣͳ࠷దԽ͸ॾѱͷࠜݯ ಋೖͱݪଇ > ݪଇ
29. KISS Keep It Simple Stupid — Clarence Leonard "Kelly" Johnson ୯७ͳํ๏ΛબͿ - ՄೳͳݶΓඪ४ͷ࣮૷Λ࢖͏ - ϥΠϒϥϦɾϑϨʔϜϫʔΫɾσβΠϯͷ༻్ΛߜΔ ඒ͍͠ɾ༏խͳίʔυ͕ಡΈ΍͍͢ͱ͸ݶΒͳ͍ ಋೖͱݪଇ > ݪଇ > KISS
30. KISS: Α͘ͳ͍ྫ return userActionLog .groupBy { it.user } .map { it.key to it.value.size } .sortedBy { it.second } .map { it.first } .takeLast(10) Ϩγʔό΍ it ͕Կ͔͸ ͢΂ͯಡ·ͳ͍ͱཧղ͕Ͱ͖ͳ͍ ಋೖͱݪଇ > ݪଇ > KISS
31. KISS: Α͘ͳ͍ྫ return userActionLog .groupBy ... .map ... .sortedBy ... .map ... .takeLast(10) Ϩγʔό΍ it ͕Կ͔͸ ͢΂ͯಡ·ͳ͍ͱཧղ͕Ͱ͖ͳ͍ ಋೖͱݪଇ > ݪଇ > KISS
32. KISS: Α͍ྫ val logCountByUser: Map<User, Int> = userActionLog .groupBy { log -> log.user } .map { (user, logs) -> user to logs.size } val userListSortedByLogCount: List<User> = logCountByUser .sortedBy { (_, messageCount) -> messageCount } .map { (userId, _) -> userId } return userListSortedByLogCount.takeLast(10) ඒ͘͠͸ͳ͍͕ɺཧղ͠΍͍͢ ಋೖͱݪଇ > ݪଇ > KISS
33. KISS: Α͍ྫ val logCountByUser: Map<User, Int> = userActionLog ... ... val userListSortedByLogCount: List<User> = logCountByUser ... ... return userListSortedByLogCount.takeLast(10) ඒ͘͠͸ͳ͍͕ɺཧղ͠΍͍͢ ಋೖͱݪଇ > ݪଇ > KISS
34. ࠓճͷ಺༰ - ಋೖ - ϘʔΠεΧ΢τϧʔϧ - YAGNIɹ - KISSɹ - ୯Ұ੹೚ݪଇ - ࣌ظঘૣͳ࠷దԽ͸ॾѱͷࠜݯ ಋೖͱݪଇ > ݪଇ > ୯Ұ੹೚ݪଇ
35. ୯Ұϝιου == ୯Ұ੹೚ʁ ϝιουͷ਺Ͱ͸੹೚͸ଌΕͳ͍ class Alviss { // May show a text, may break the device, may launch a rocket, // may ... fun doEverything(state: UniverseState) } ಋೖͱݪଇ > ݪଇ > ୯Ұ੹೚ݪଇ
36. ୯Ұ੹೚ݪଇ A class should have only one reason to change. — Robert C. Martin ̎ͭҎ্ͷػೳΛࠞͥͯ͸͍͚ͳ͍ ಋೖͱݪଇ > ݪଇ > ୯Ұ੹೚ݪଇ
37. ୯Ұ੹೚ݪଇ: Α͘ͳ͍ྫ 1/2 ਤॻؗͷॻ੶ି͠ग़͠ঢ়ଶ ಋೖͱݪଇ > ݪଇ > ୯Ұ੹೚ݪଇ
38. ୯Ұ੹೚ݪଇ: Α͘ͳ͍ྫ 2/2 class LibraryBookRentalData( val bookIds: MutableList<Int>, val bookNames: MutableList<String>, val bookIdToRenterNameMap: MutableMap<Int, String>, val bookIdToDueDateMap: MutableMap<Int, Date>, ... ) { fun findRenterName(bookName: String): String? fun findDueDate(bookName: String): Date? ... ಋೖͱݪଇ > ݪଇ > ୯Ұ੹೚ݪଇ
39. ୯Ұ੹೚ݪଇ: վળҊ 1/2 ΫϥεΛΤϯςΟςΟ͝ͱʹ෼ׂ͢Δ ಋೖͱݪଇ > ݪଇ > ୯Ұ੹೚ݪଇ
40. ୯Ұ੹೚ݪଇ: վળҊ 2/2 data class BookData(val id: Int, val name: String, ...) data class UserData(val name: String, ...) class CirculationRecord( val onLoanBookEntries: MutableMap<BookData, Entry> ) { data class Entry(val renter: UserData, val dueDate: Date) ಋೖͱݪଇ > ݪଇ > ୯Ұ੹೚ݪଇ
41. ੹೚ͷ෼ׂ ΫϥεΛ෼ׂ͢Δ - ΤϯςΟςΟ͝ͱʹϞσϧΛ෼͚Δ - ϨΠϠ΍ίϯϙʔωϯτ͝ͱʹϩδοΫΛ෼͚Δ - ର৅ͷσʔλܕ͝ͱʹϢʔςΟϦςΟΛ෼͚Δ ಋೖͱݪଇ > ݪଇ > ୯Ұ੹೚ݪଇ
42. ੹೚ൣғͷ֬ೝํ๏ Ϋϥε͕͍ͯ͠Δ͜ͱΛྻڍ → ཁ໿Λॻ͘ ෼ׂΛߟྀ͢΂͖ঢ়گ: - ཁ໿Λॻ͘ͷ͕೉͍͠ - ໊લʹൺ΂ͯཁ໿͕ංେʹͳΔ ಋೖͱݪଇ > ݪଇ > ୯Ұ੹೚ݪଇ
43. ࠓճͷ಺༰ - ಋೖ - ϘʔΠεΧ΢τϧʔϧ - YAGNIɹ - KISSɹ - ୯Ұ੹೚ݪଇ - ࣌ظঘૣͳ࠷దԽ͸ॾѱͷࠜݯ ಋೖͱݪଇ > ݪଇ
44. ࣌ظঘૣͳ࠷దԽ͸ॾѱͷࠜݯ 1/2 We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil. — Structured Programming with go to Statements, Donald Knuth ಋೖͱݪଇ > ݪଇ > ࣌ظঘૣͳ࠷దԽ͸ॾѱͷࠜݯ
45. ࣌ظঘૣͳ࠷దԽ͸ॾѱͷࠜݯ 2/2 Α͍࠷దԽ: ίʔυΛ୯७ʹ͢Δ࠷దԽ Α͘ͳ͍࠷దԽ: ίʔυΛෳࡶʹ͢Δ࠷దԽ ಋೖͱݪଇ > ݪଇ > ࣌ظঘૣͳ࠷దԽ͸ॾѱͷࠜݯ
46. Α͍࠷దԽͷྫ ࠷దԽલ: val data = arrayList.find { data -> data.key == expectedKey } ࠷దԽޙ: val data = hashMap[expectedKey] ίʔυΛ୯७ʹͭͭ͠ ܭࢉྔΛݮΒ͢ ಋೖͱݪଇ > ݪଇ > ࣌ظঘૣͳ࠷దԽ͸ॾѱͷࠜݯ
47. ίʔυΛෳࡶʹ͢Δ࠷దԽ 1/2 Yet we should not pass up our opportunities in that critical 3% — Donald Knuth ಋೖͱݪଇ > ݪଇ > ࣌ظঘૣͳ࠷దԽ͸ॾѱͷࠜݯ
48. ίʔυΛෳࡶʹ͢Δ࠷దԽ 1/2 - ՄมΦϒδΣΫτͷ࠶ར༻ - Πϯελϯεϓʔϧ - ஗ԆॳظԽ - Ωϟογϡ ϓϥοτϑΥʔϜͷαϙʔτ͔ϓϩϑΝΠϦϯά͕ඞཁ ಋೖͱݪଇ > ݪଇ > ࣌ظঘૣͳ࠷దԽ͸ॾѱͷࠜݯ
49. ࠷దԽͷฐ֐ ୯७Խͷ๦͛ʹͳΔ - ΦϓςΟϚΠβͷ΄͏͕ੑೳ͕Α͍͜ͱ΋ Φʔόϔουίετ͕͔͔Δ - Ωϟογϡ: Ωϟογϡϛε཰ ΞΫηε࣌ؒ - ஗ԆॳظԽ: (ಉظతͳ) ΠϯελϯενΣοΫ ಋೖͱݪଇ > ݪଇ > ࣌ظঘૣͳ࠷దԽ͸ॾѱͷࠜݯ
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