Swift の struct の stored property は var にしよう

potatotips#39 という勉強会で発表したものです。セリフ付きでQiitaにもアップしています。http://qiita.com/omochimetaru/items/7265e440418b38088ccb

Transcript

1. Swift ͷ struct ͷ stored property ͸ var ʹ͠Α͏ omochimetaru @
2. ࣗݾ঺հ • ID: omochimetaru @ Qoncept, Inc • Swift, Kotlin, C++, TypeScript, C#, Ruby, Python • http://qiita.com/omochimetaru • Android։ൃΛड஫͔ͨ͠ΒKotlinΛΨοπϦ... • null҆શΛޡղ͍ͯ͠Δਓୡ΁ͷϝοηʔδ • SwiftͷδΣωϦοΫͳϓϩτίϧͷม਺͸...
3. ໎͍ͬͯ·ͤΜ͔ʁ struct SVCat { var name: String var age: Int } struct SLCat { let name: String let age: Int }
4. େৎ෉͔ͩΒ var ʹͯ͠ʂ
5. > Immutable ͳઃܭ͸ྑ͍͜ͱ ͔ͩΒɺlet ʹͨ͠ํ͕ྑ͍ʁ
6. Struct ͳΒ var Ͱ΋ immutable (ͱΈͳͤΔ) ͔Β େৎ෉ʂ
7. Immutable ͷ֬ೝ • શ͕ͯletͷΫϥε • มߋ༻ͷϏϧμʔ
8. Immutable ͷ֬ೝ class CCat { init(name: String, age: Int) { self.name = name self.age = age } let name: String let age: Int } class MutableCCat { init(cat: CCat) { self.name = cat.name self.age = cat.age } var name: String var age: Int var cat: CCat { return CCat(name: name, age: age) } }
9. var࣋ͪstruct = immutable class + builder
10. Immutable Λײ͡Δ structBreeder.cat.name = "tama"
11. Immutable Λײ͡Δ structBreeder.cat.name = "tama" // ↑↓ var cat = structBreeder.cat cat.name = "tama" structBreeder.cat = cat
12. Immutable Λײ͡Δ structBreeder.cat.name = "tama" // ↑↓ var cat = structBreeder.cat cat.name = "tama" structBreeder.cat = cat // ↑↓ let cat = MutableCCat(cat: classBreeder.cat) cat.name = "tama" classBreeder.cat = cat.cat
13. > ಉ͡ΠϯελϯεΛ มߋ͍ͯ͠Δ͡Όͳ͍͔ʂ
14. ಉ͡ΠϯελϯεΛมߋͨ͠ͷ͔ɺ ৽͍͠Πϯελϯεʹ ࠩ͠ସ͑ͨͷ͔͸ɺ ڞ༗͞Ε͍ͯͳ͚Ε͹۠ผͰ͖ͳ͍ɻ
15. ڞ༗ͱmutability
16. mutableΫϥεΛڞ༗͢Δ͔Β ࠔͬͨ͜ͱʹͳΔ print(classBreeder1.cat.name) // cat1 is mike classBreeder2.cat = classBreeder1.cat classBreeder2.cat.name = "tama" print(classBreeder2.cat.name) // cat2 is tama print(classBreeder1.cat.name) // cat1 is tama ← ! • ଞͷڞ༗ऀ͔Βҙਤͤͣมߋ͕༩͑ΒΕΔ
17. struct͸ڞ༗Ͱ͖ͳ͍͔Βେৎ෉ print(structBreeder1.cat.name) // cat1 is mike structBreeder2.cat = structBreeder1.cat structBreeder2.cat.name = "tama" print(structBreeder2.cat.name) // cat2 is tama print(structBreeder1.cat.name) // cat1 is mike ← ! • ίϐʔʹΑ࣮ͬͯମ͕૿͑ΔͨΊৗʹઐ༗͢Δ
18. ·ͱΊ • struct͸ڞ༗Ͱ͖ͳ͍ • ͔ͩΒ࣮ମͷมߋͱɺ৽͍࣮͠ମ΁ͷࠩ͠ସ͕͑౳Ձ • ͔ͩΒ var Ͱ΋ immutable class ͱ౳Ձ • var Ͱ΋҆શ͔ͩΒ var ʹ͓ͯ͜͠͏ɻ
19. ଓ͖ͷ࿩ • ࠙਌ձ • Discord (SlackΈ͍ͨͳ΍ͭ) ͷ iOS αʔόʔͰ • ؅ཧऀ: SwiftϨλʔͷ @_mono ͞Μ • ΞΫηε: ʮDiscord iOSʯͰݕࡧ