読みやすいコードの書き方 第 7 回 / Code readability: Session 7 (ver. 2, Ja)

第 7 回: 依存関係 II

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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΍͍͢ίʔυͷॻ͖ํˡୈ 7 ճ ґଘؔ܎ ‐‐
2. લճͷ͓͞Β͍: ݁߹౓ ऑ͍݁߹Λ࢖͏ - ελϯϓ݁߹ɾσʔλ݁߹Λҙࣝͯ͠࢖͏ ஫ҙ͢Δ΂͖݁߹ - ಺༰݁߹: ಺෦ͷৄࡉͳಈ࡞ʹґଘ͢Δؔ܎ - ڞ௨݁߹ɾ֎෦݁߹: Մมͳάϩʔόϧσʔλ࢖͏ؔ܎ - ੍ޚ݁߹: ʮԿΛ͢Δ͔ʯΛҾ਺ͰܾΊΔؔ܎
3. ߨٛͷߏ੒ - ಋೖͱݪଇ - ࣗવݴޠ: ໋໊, ίϝϯτ - ܕͷߏ଄: ঢ়ଶ, ؔ਺ - ܕؒͷߏ଄: ґଘؔ܎I, ґଘؔ܎II - ϨϏϡʔ ґଘؔ܎
4. ґଘؔ܎ IɾII ͷ಺༰ ґଘؔ܎ I: - ݁߹౓ ґଘؔ܎ II: - ํ޲ - ॏෳ - ໌ࣔੑ ґଘؔ܎ > ํ޲
5. ґଘͷํ޲ ՄೳͳݶΓඇ८ճʹ͢Δ A C B A C B ґଘؔ܎ > ํ޲
6. ޷·͍͠ґଘͷํ޲ - ݺͼग़͠ݩ → ݺͼग़͠ઌ - ৄࡉ → ந৅ - ෳࡶ → ୯७ - Մม → ෆม - ΞϧΰϦζϜ → σʔλߏ଄ - සൟʹߋ৽͞ΕΔϨΠϠ → ҆ఆతͳϨΠϠ ґଘؔ܎ > ํ޲
7. ޷·͍͠ґଘͷํ޲ - ݺͼग़͠ݩ → ݺͼग़͠ઌ - ৄࡉ → ந৅ - ෳࡶ → ୯७ ґଘؔ܎ > ํ޲
8. ޷·͍͠ґଘͷํ޲ - ݺͼग़͠ݩ → ݺͼग़͠ઌ - ৄࡉ → ந৅ - ෳࡶ → ୯७ ґଘؔ܎ > ํ޲ > ݺͼग़͠ݩ → ݺͼग़͠ઌ
9. ݺͼग़͠ݩ΁ͷґଘ: ʮΑ͘ͳ͍ʯྫ 1/2 class MediaViewPresenter { fun getVideoUri(): Uri = ... fun playVideo() { videoPlayerView.play(this) ... class VideoPlayerView { fun play(presenter: MediaViewPresenter) { val uri = presenter.getVideoUri() ґଘؔ܎ > ํ޲ > ݺͼग़͠ݩ → ݺͼग़͠ઌ
10. ݺͼग़͠ݩ΁ͷґଘ: ʮΑ͘ͳ͍ʯྫ 2/2 MediaViewPresenter fun getVideoUri VideoPlayerView fun play play getVideoUri ґଘؔ܎ > ํ޲ > ݺͼग़͠ݩ → ݺͼग़͠ઌ
11. ݺͼग़͠ݩ΁ͷґଘ: Կ͕ʮΑ͘ͳ͍ʯ͔ ಈ࡞Λ೺Ѳ͠ʹ͍͘ playVideo ͷॲཧͷྲྀΕ͕୯७Ͱͳ͍ มߋͷӨڹൣғ͕େ͖͍ MediaViewPresenter ͷมߋ͕ VideoPlayerView ʹӨڹΛ༩͑Δ ςετ͕ॻ͖ʹ͍͘ VideoPlayerView ͷϞοΫΦϒδΣΫτ͕ෳࡶʹͳΔ ґଘؔ܎ > ํ޲ > ݺͼग़͠ݩ → ݺͼग़͠ઌ
12. ݺͼग़͠ݩ΁ͷґଘ: վળํ๏ ෆཁͳίʔϧόοΫΛ࡟আ͢Δ - Ҿ਺ͱͯ͠஋Λ౉͢ - খ͞ͳΫϥεͱͯ͠நग़͢Δ ґଘؔ܎ > ํ޲ > ݺͼग़͠ݩ → ݺͼग़͠ઌ
13. ݺͼग़͠ݩ΁ͷґଘ: վળํ๏ ෆཁͳίʔϧόοΫΛ࡟আ͢Δ - Ҿ਺ͱͯ͠஋Λ౉͢ - খ͞ͳΫϥεͱͯ͠நग़͢Δ ґଘؔ܎ > ํ޲ > ݺͼग़͠ݩ → ݺͼग़͠ઌ
14. Ҿ਺ͱͯ͠஋Λ౉͢ class MediaViewPresenter { fun getVideoUri(): Uri = ... fun playVideo() { videoPlayerView.play(this) ... class VideoPlayerView { fun play(presenter: MediaViewPresenter) { val uri = presenter.getVideoUri() ґଘؔ܎ > ํ޲ > ݺͼग़͠ݩ → ݺͼग़͠ઌ
15. Ҿ਺ͱͯ͠஋Λ౉͢ class MediaViewPresenter { fun getVideoUri(): Uri = ... fun playVideo() { videoPlayerView.play(getVideoUri()) ... class VideoPlayerView { fun play(videoUri: Uri) { ... ґଘؔ܎ > ํ޲ > ݺͼग़͠ݩ → ݺͼग़͠ઌ
16. ݺͼग़͠ݩ΁ͷґଘ: վળํ๏ ෆཁͳίʔϧόοΫΛ࡟আ͢Δ - Ҿ਺ͱͯ͠஋Λ౉͢ - খ͞ͳΫϥεͱͯ͠நग़͢Δ ґଘؔ܎ > ํ޲ > ݺͼग़͠ݩ → ݺͼग़͠ઌ
17. খ͞ͳΫϥεͱͯ͠நग़͢Δ ඇಉظʹ݁ՌΛॲཧ͢Δ৔߹͸஋Λ౉ͤͳ͍ ґଘઌͷίʔυΛΫϥεͱͯ͠நग़͢Δ ґଘؔ܎ > ํ޲ > ݺͼग़͠ݩ → ݺͼग़͠ઌ
18. খ͞ͳΫϥεͱͯ͠நग़͢Δ: εςοϓ 1 ίʔϧόοΫ෦෼Λ໊લͷ͍ͭͨ಺෦Ϋϥεʹ͢Δ MediaViewPresenter VideoPlayerView VideoUriProvider fun getVideoUri ґଘؔ܎ > ํ޲ > ݺͼग़͠ݩ → ݺͼग़͠ઌ
19. খ͞ͳΫϥεͱͯ͠நग़͢Δ: εςοϓ 2 ಺෦ΫϥεΛ֎෦Ϋϥεͷ֎ʹҠಈ͢Δ MediaViewPresenter VideoPlayerView VideoUriProvider fun getVideoUri ґଘؔ܎ > ํ޲ > ݺͼग़͠ݩ → ݺͼग़͠ઌ
20. ݺͼग़͠ݩ΁ͷґଘ: վળํ๏ ෆཁͳίʔϧόοΫΛ࡟আ͢Δ - Ҿ਺ͱͯ͠஋Λ౉͢ - খ͞ͳΫϥεͱͯ͠நग़͢Δ ґଘؔ܎ > ํ޲ > ݺͼग़͠ݩ → ݺͼग़͠ઌ
21. ݺͼग़͠ݩ΁ͷґଘ: ྫ֎ ݺͼग़͠ݩ΁ͷґଘ͕ආ͚ΒΕͳ͍ঢ়گ͸͋Δ - ඇಉظݺͼग़͠: εϨουɾΠϕϯτϦεφ - ϢʔςΟϦςΟߴ֊ؔ਺: List.forEach ґଘؔ܎ > ํ޲ > ݺͼग़͠ݩ → ݺͼग़͠ઌ
22. ඇಉظݺͼग़͠ͷ؇࿨ ίʔϧόοΫͷར༻໨తɾϥΠϑαΠΫϧɾείʔϓΛ੍ݶ͢Δ - ϓϩϛεύλʔϯɾϑϡʔνϟʔΦϒδΣΫτ ඇಉظॲཧͷݴޠػೳɾϥΠϒϥϦΛ࢖͏ - ίϧʔνϯɾΞΫλʔɾasync/await ґଘؔ܎ > ํ޲ > ݺͼग़͠ݩ → ݺͼग़͠ઌ
23. ޷·͍͠ґଘͷํ޲ - ݺͼग़͠ݩ → ݺͼग़͠ઌ - ৄࡉ → ந৅ - ෳࡶ → ୯७ ґଘؔ܎ > ํ޲ > ৄࡉ → ந৅
24. ৄࡉ΁ͷґଘ ࢠΫϥε΁ͷґଘΛ͠ͳ͍ = this ΍ self ͷܕνΣοΫɾμ΢ϯΩϟετΛආ͚Δ ґଘؔ܎ > ํ޲ > ৄࡉ → ந৅
25. ৄࡉ΁ͷґଘ: ʮΑ͘ͳ͍ʯྫ open class IntList { fun addElement(value: Int) { if (this is ArrayIntList) { ... } else { ... ... class ArrayIntList: IntList() { ... ґଘؔ܎ > ํ޲ > ৄࡉ → ந৅
26. ৄࡉ΁ͷґଘ: Կ͕ʮΑ͘ͳ͍ʯ͔ ੹೚ͷൣғ͕ᐆດ มߋʹର͢Δؤ݈ੑ͕௿͍ - ࢠΫϥεͷ࢓༷ͷมߋ - ৽͍͠ࢠΫϥεͷ௥Ճ ґଘؔ܎ > ํ޲ > ৄࡉ → ந৅
27. ৄࡉ΁ͷґଘ: मਖ਼ྫ ΦʔόʔϥΠυΛ࢖ͬͯμ΢ϯΩϟετΛආ͚Δ open class IntList { open fun addElement(value: Int) { ... class ArrayIntList: IntList() { override fun addElement(value: Int) { ... ґଘؔ܎ > ํ޲ > ৄࡉ → ந৅
28. ޷·͍͠ґଘͷํ޲ - ݺͼग़͠ݩ → ݺͼग़͠ઌ - ৄࡉ → ந৅ - ෳࡶ → ୯७ ґଘؔ܎ > ํ޲ > ෳࡶ → ୯७
29. ෳࡶͳίʔυ΁ͷґଘ: ʮΑ͘ͳ͍ʯྫ class UserData( val userId: UserId, ... ) class UserDataRequester { fun obtainFromServer(): UserData { ... ґଘؔ܎ > ํ޲ > ෳࡶ → ୯७
30. ෳࡶͳίʔυ΁ͷґଘ: ʮΑ͘ͳ͍ʯྫ class UserData( val userId: UserId, ... val requester: UserDataRequester ) class UserDataRequester { fun obtainFromServer(): UserData { ... ґଘؔ܎ > ํ޲ > ෳࡶ → ୯७
31. ෳࡶͳίʔυ΁ͷґଘ: Կ͕ʮΑ͘ͳ͍ʯ͔ ෳࡶͳίʔυͷείʔϓɾϥΠϑαΠΫϧɾࢀর͕؅ཧ͕ࠔ೉ - ୯७ͳίʔυ: είʔϓ΍ϥΠϑαΠΫϧ͕ ଟ༷ - ෳࡶͳίʔυ: είʔϓ΍ϥΠϑαΠΫϧͷ ݫີͳ؅ཧ͕ඞཁ ؤ݈ੑΛଛͳ͏ - ϦιʔεͷϦʔΫͷݪҼʹͳΓ͏Δ - ୯७ͳίʔυͷ҉໧తͳલఏ৚͕݅૿͑Δ ґଘؔ܎ > ํ޲ > ෳࡶ → ୯७
32. ෳࡶͳίʔυ΁ͷґଘ: վળํ๏ ෳࡶͳίʔυ΁ͷࢀরΛ୯७ʹ࡟আ͢Δ - ෳࡶͳίʔυ͕ඞཁͳΒɺͦͷࢀরΛ໌ࣔతʹ౉͢ class UserData( val userId: UserId, ... ) ґଘؔ܎ > ํ޲ > ෳࡶ → ୯७
33. ෳࡶͳίʔυ΁ͷґଘ: ྫ֎ ෳࡶͳίʔυ΁ͷґଘ͕ආ͚ΒΕͳ͍ঢ়گ΋͋Γ͑Δ - ϝσΟΤʔλύλʔϯ - ΞμϓλʔɾϑΝαʔυ - σʔλόΠϯσΟϯά ՄೳͳݶΓ༻్ɾείʔϓΛݶఆ͢Δ ґଘؔ܎ > ํ޲ > ෳࡶ → ୯७
34. ޷·͍͠ґଘͷํ޲ - ݺͼग़͠ݩ → ݺͼग़͠ઌ - ৄࡉ → ந৅ - ෳࡶ → ୯७ ґଘؔ܎ > ํ޲ > ·ͱΊ
35. ґଘͷํ޲: ·ͱΊ ґଘ͸Ұํ޲ʹ͢Δ - ݺͼग़͠ݩ → ݺͼग़͠ઌ - ෳࡶɾৄࡉɾՄม → ୯७ɾந৅ɾෆม ྫ֎: ඇಉظݺͼग़͠ɾϝσΟΤʔλύλʔϯ౳ ྫ֎Λ࢖͏৔߹Ͱ΋ ໨తɾείʔϓɾϥΠϑαΠΫϧΛ੍ݶ͢Δ ґଘؔ܎ > ํ޲ > ·ͱΊ
36. ґଘؔ܎ IɾII ͷ಺༰ ґଘؔ܎ I: - ݁߹౓ ґଘؔ܎ II: - ํ޲ - ॏෳ - ໌ࣔੑ ґଘؔ܎ > ॏෳ
37. ґଘͷॏෳ ਺चͭͳ͗ͷґଘ - ωετ͞Εͨɾ௚઀ࢀরͰͳ͍ґଘ ॏෳͨ͠ґଘؔ܎ͷηοτ - N:M ͷґଘ ґଘؔ܎ > ॏෳ
38. ґଘͷॏෳ ਺चͭͳ͗ͷґଘ - ωετ͞Εͨɾ௚઀ࢀরͰͳ͍ґଘ ॏෳͨ͠ґଘؔ܎ͷηοτ - N:M ͷґଘ ґଘؔ܎ > ॏෳ
39. ਺चͭͳ͗ͷґଘ ࢀরͷऔಘͷͨΊ͚ͩʹແؔ܎ͳίʔυʹґଘ͠ͳ͍ MessageTextPresenter TimestampPresenter (MessageDataProvider ) MessageDataProvider ґଘؔ܎ > ॏෳ > ਺चͭͳ͗ͷґଘ
40. ਺चͭͳ͗ͷґଘ: ʮΑ͘ͳ͍ʯྫ class TimestampPresenter { val dataProvider: MessageDataProvider = ... fun invalidateViews() { // Update timestamp by `dataProvider` ... class MessageTextPresenter { val timestampPresenter: TimestampPresenter = ... fun invalidateViews() { val messageData = timestampPresenter.dataProvider... // Update message text view by `messageData` ґଘؔ܎ > ॏෳ > ਺चͭͳ͗ͷґଘ
41. ਺चͭͳ͗ͷґଘ: Կ͕ʮΑ͘ͳ͍ʯ͔ ෆཁͳґଘؔ܎ MessageTextPresenter ͸ຊདྷ TimestampPresenter ͱ͸ؔ܎ͳ͍ ؒ઀తͳґଘؔ܎ MessageTextPresenter ͱ MessageDataProvider ͷؔ܎͕ෆ໌ྎ ґଘؔ܎ > ॏෳ > ਺चͭͳ͗ͷґଘ
42. ਺चͭͳ͗ͷґଘ: मਖ਼ํ๏ ґଘͷωετΛ௚઀తͳґଘؔ܎Ͱஔ͖׵͑Δ MessageTextPresenter TimestampPresenter MessageDataProvider ґଘؔ܎ > ॏෳ > ਺चͭͳ͗ͷґଘ
43. ਺चͭͳ͗ͷґଘ: मਖ਼ྫ class TimestampPresenter { val dataProvider: MessageDataProvider = ... fun invalidateViews() { // Update timestamp by `dataProvider` ... class MessageTextPresenter { val dataProvider: MessageDataProvider = ... fun invalidateViews() { // Update message text view by `dataProvider` ґଘؔ܎ > ॏෳ > ਺चͭͳ͗ͷґଘ
44. ґଘͷॏෳ ਺चͭͳ͗ͷґଘ - ωετ͞Εͨɾ௚઀ࢀরͰͳ͍ґଘ ॏෳͨ͠ґଘؔ܎ͷηοτ - N:M ͷґଘ ґଘؔ܎ > ॏෳ > ॏෳͨ͠ґଘؔ܎ͷηοτ
45. ॏෳͨ͠ґଘؔ܎ͷηοτ ʮෳ਺ͷಉ͡Ϋϥεͷू߹ʹґଘ͢Δʯ͜ͱΛආ͚Δ MessageTextPresenter TimestampPresenter LocalMessageDataProvider RemoteMessageDataProvider ґଘؔ܎ > ॏෳ > ॏෳͨ͠ґଘؔ܎ͷηοτ
46. ॏෳͨ͠ґଘؔ܎ͷηοτ: Կ͕ʮΑ͘ͳ͍ʯ͔ ίʔυͷมߋʹରͯ͠੬ऑ - ґଘݩɾґଘઌʹΫϥεΛ௥Ճͨ͠৔߹ʹߋ৽Λ๨ΕΔՄೳੑ - ίʔυͷॏෳ͕ݪҼ ґଘؔ܎ > ॏෳ > ॏෳͨ͠ґଘؔ܎ͷηοτ
47. ॏෳͨ͠ґଘؔ܎ͷηοτ: मਖ਼ํ๏ ґଘઌΛ·ͱΊΔதؒϨΠϠΛ࡞੒͢Δ MessageTextPresenter TimestampPresenter LocalMessageDataProvider RemoteMessageDataProvider MessageDataProvider ґଘؔ܎ > ॏෳ > ॏෳͨ͠ґଘؔ܎ͷηοτ
48. ॏෳͨ͠ґଘؔ܎ͷηοτ: मਖ਼͢Δࡍͷ஫ҙ఺ ෆཁͳ͏ͪ͸தؒϨΠϠΛ࡞Βͳ͍ "YAGNI" ͱ "KISS" Λ৺͕͚Δ Ӆ͍ͯ͠Δ૚ΛݟͤΔʮτϯωϧʯΛ࡞Βͳ͍ MessageDataProvider ʹ public ͳ serverMessageDataProvider Λ ࡞Βͳ͍ ґଘؔ܎ > ॏෳ > ॏෳͨ͠ґଘؔ܎ͷηοτ
49. ґଘͷॏෳ: ·ͱΊ - ࢀরΛऔಘ͢ΔͨΊ͚ͩʹແؔ܎ͳΫϥεʹґଘ͠ͳ͍ - ґଘؔ܎ͷηοτ͕ॏෳͨ͠৔߹͸தؒϨΠϠΛ࡞Δ ґଘؔ܎ > ॏෳ > ·ͱΊ
50. ґଘؔ܎ IɾII ͷ಺༰ ґଘؔ܎ I: - ݁߹౓ ґଘؔ܎ II: - ํ޲ - ॏෳ - ໌ࣔੑ ґଘؔ܎ > ໌ࣔੑ
51. ҉໧తͳґଘؔ܎ 1/3 Ϋϥεͷఆ͚ٛͩͰ͸ൃݟͰ͖ͳ͍ґଘؔ܎ interface Interface class Implementation : Interface class Caller(val interface: Interface) Caller ͸ Implementation ͷมߋͷӨڹΛड͚͏Δ Caller(Implementation()) ґଘؔ܎ > ໌ࣔੑ
52. ҉໧తͳґଘؔ܎ 2/3 ΫϥεਤͰදݱ͞Εͳ͍ Caller Interface Implementation ґଘؔ܎ > ໌ࣔੑ
53. ҉໧తͳґଘؔ܎ 3/3 ҉໧తͳґଘؔ܎Λආ͚ɺ໌ࣔతͳґଘؔ܎Λ࢖͏ ӨڹൣғΛΘ͔Γ΍͘͢͢Δ ʮऑ͍݁߹ʯͱ͸ҟͳΔ - ґଘΛऑͨͭ͘͠΋ΓͰɺ҉໧తʹͯ͠͸ͳΒͳ͍ ґଘؔ܎ > ໌ࣔੑ
54. ҉໧తͳґଘؔ܎: ྫ - ա౓ͳந৅Խ - ҉໧తͳҾ਺ͷมҬ ґଘؔ܎ > ໌ࣔੑ
55. ҉໧తͳґଘؔ܎: ྫ - ա౓ͳந৅Խ - ҉໧తͳҾ਺ͷมҬ ґଘؔ܎ > ໌ࣔੑ > ҉໧తͳมҬ
56. ա౓ͳந৅Խ ݺͼग़͠ଆ͕ࢠΫϥεʹ҉໧తʹґଘ͍ͯ͠Δ ProfilePresenter MessagePresenter StringProvider ProfileDataRepository MessageDataRepository ґଘؔ܎ > ໌ࣔੑ > ա౓ͳந৅Խ
57. ա౓ͳந৅Խ: ʮΑ͘ͳ͍ʯྫ interface StringProvider { fun queryString(id: Int): String } class ProfileDataRepository : StringProvider { /** Returns user name of the given [userId] */ override fun queryString(userId: Int): String = ... } class ProfilePresenter(val nameProvider: StringProvider, ...) { fun updateProfileView(userId: Int) { userNameView.text = nameProvider.queryString(userId) ... ґଘؔ܎ > ໌ࣔੑ > ա౓ͳந৅Խ
58. ա౓ͳந৅Խ: Կ͕ʮΑ͘ͳ͍ʯ͔ ॲཧͷྲྀΕΛ௥੻͢Δ͜ͱ͕ࠔ೉ ίϯετϥΫλͷݺͼग़͠ݩΛݟͳ͍ͱίʔυΛḷΕͳ͍ ؒҧͬͨΠϯελϯεΛ౉͢Մೳੑ͕͋Δ MessageDataRepository Λ౉ͯ͠΋ίʔυͱͯ͠͸༗ޮ ґଘؔ܎ > ໌ࣔੑ > ա౓ͳந৅Խ
59. ա౓ͳந৅Խ: मਖ਼ํ๏ ෆཁͳܧঝؔ܎͸࡟আ͢Δ ਌ΫϥεɾΠϯλʔϑΣΠεΛ࡟আ͠ɺ௚઀ࢀর͢Δ ProfilePresenter MessagePresenter ProfileDataRepository MessageDataRepository ґଘؔ܎ > ໌ࣔੑ > ա౓ͳந৅Խ
60. ա౓ͳந৅Խ: मਖ਼ྫ class ProfileDataRepository { fun queryUserName(userId: Int): String = ... } class ProfilePresenter(val repository: ProfileDataRepository, ...) { fun updateProfileView(userId: Int) { userNameView.text = repository.queryUserName(userId) ... ґଘؔ܎ > ໌ࣔੑ > ա౓ͳந৅Խ
61. ա౓ͳந৅Խ: ஫ҙ͢Δ΂͖఺ 1/2 ܧঝΛ࢖͏໨తΛ໌֬ʹ͢Δ - ଟ૬ੑͷར༻ - ௚࿨ܕͷར༻: sealed class - ґଘੑٯస΍࣮૷ͷ෼཭: ϞδϡʔϧԽɾϥΠϒϥϦԽ ґଘؔ܎ > ໌ࣔੑ > ա౓ͳந৅Խ
62. ա౓ͳந৅Խ: ஫ҙ͢Δ΂͖఺ 2/2 ίʔυͷڞ௨ԽͷͨΊ͚ͩʹܧঝΛ࢖Θͳ͍ - ू໿΍ίϯϙδγϣϯͷར༻Λݕ౼ ଟ૬ੑ͕໨తͷ৔߹ɺଞͷ࣮ݱํ๏΋ݕ౼͢Δ - ύϥϝτϦοΫଟ૬: δΣωϦΫε౳ - ΞυϗοΫଟ૬: ΦʔόʔϩʔυɾܕΫϥε౳ ґଘؔ܎ > ໌ࣔੑ > ա౓ͳந৅Խ
63. ҉໧తͳґଘؔ܎: ྫ - ա౓ͳந৅Խ - ҉໧తͳҾ਺ͷมҬ ґଘؔ܎ > ໌ࣔੑ > ҉໧తͳมҬ
64. ҉໧తͳҾ਺ͷมҬ: ʮΑ͘ͳ͍ʯྫ ໰୊: ҎԼͷίʔυͷʮΑ͘ͳ͍ʯ఺͸ʁ fun setViewBackgroundColor(colorString: String) { val colorCode = when(colorString) { "red" -> 0xFF0000 "green" -> 0x00FF00 else -> 0x000000 } view.setBackgroundColor(colorCode) } ґଘؔ܎ > ໌ࣔੑ > ҉໧తͳมҬ
65. ҉໧తͳҾ਺ͷมҬ: Կ͕ʮΑ͘ͳ͍ʯ͔ ݺͼग़͠ݩɾઌ͕҉໧తͳ੍໿Ͱ݁͹Ε͍ͯΔ ༗ޮͳ࣮Ҿ਺͸Կ͔Λ஌Δඞཁ͕͋Δ "blue"ɾ"RED"ɾ"FF0000" ͸ແޮ ࢓༷ͷมߋʹରͯ͠੬ऑ ৭Λ௥Ճɾ࡟আͨ͠৔߹ʹݺͼग़͠ݩͷมߋ͕ඞཁ ґଘؔ܎ > ໌ࣔੑ > ҉໧తͳมҬ
66. ҉໧తͳҾ਺ͷมҬ: मਖ਼ํ๏ มҬΛࣔͨ͢ΊͷϞσϧΛ࡞Δ enum class BackgroundColor(val colorCode: Int) { RED(0xFF0000), GREEN(0x00FF00) } fun setViewBackgroundColor(color: BackgroundColor) { view.setBackgroundColor(color.colorCode) } ґଘؔ܎ > ໌ࣔੑ > ҉໧తͳมҬ
67. ґଘؔ܎ͷ໌ࣔੑ: ·ͱΊ ໌ࣔతͳґଘؔ܎Λ࢖͏ - ΫϥεఆٛɾਤͰཧղͰ͖Δґଘؔ܎ʹ͢Δ - ʮऑ͍݁߹ʯͱࠞಉ͠ͳ͍ ґଘؔ܎Λ໌ࣔతʹ͢Δํ๏ྫ - ա౓ͳந৅ԽϨΠϠΛ࡟আ͢Δ - มҬΛ໌ࣔ͢ΔϞσϧΛ࡞Δ ґଘؔ܎ > ໌ࣔੑ > ·ͱΊ
68. ·ͱΊ ɹ ݁߹౓: ಺༰ɾڞ௨ɾ֎෦ɾ੍ޚ݁߹Λ؇࿨͢Δ ํ޲: Ұํ޲ʹ͢Δɾ८ճΛখ͍͞ൣғʹ੍ݶ͢Δ ॏෳ: ਺चͭͳ͗ͷґଘ΍ηοτͷॏෳΛආ͚Δ ໌ࣔੑ: ΫϥεͷఆٛͰཧղͰ͖Δґଘؔ܎Λ࢖͏ ґଘؔ܎ > ·ͱΊ