Opaque Result Typeの解説

Source: https://gist.github.com/omochi/0039ceac42f7da84caf9ff6d5d92a278

Transcript

1. Opaque Result Typeͷղઆ omochimetaru Θ͍Θ͍swiftc #11 1
2. 5ඵͳΒ 2
3. ͜ΕΛݟͯ Proposal SE-0244 Opaque Result Type https://github.com/apple/swift-evolution/blob/ master/proposals/0244-opaque-result-types.md 3
4. ͜ΕΛݟͯ Swift 5.1 ʹಋೖ͞ΕΔ Opaque Result Type ͱ͸ Կ͔ https://qiita.com/koher/items/ 338d2f2d0c4731e3508f 4
5. ղઆ͢ΔͳΒ 5
6. Opaque Result Type ύϑΥʔϚϯεΛอͪͭͭɺ ਅͷܕΛӅṭ͢Δ৽ػೳ 6
7. ಈػ 7
8. ਅͷܕΛӅṭ ʮ͋ΔϓϩτίϧΛฦ͢ʯͱݴ͍͍ͨ͜ͱ͕͋Δ func loadUsers() -> ??? // Sequence of User 8
9. ۩ମతͳܕΛฦͯ͠͠·͏ͱকདྷมߋͰ͖ͳ͍ // ver 1.0.0 func loadUsers() -> [User] // ver 1.1.0 func loadUsers() -> LazySequence<User> 9
10. ैདྷͷํ๏ Type Erasure΍ExistentialͰฦ͢ func loadUsers() -> AnySequence<User> • ܕͷਖ਼͠͞Λଛͳ͏ • ύϑΥʔϚϯεΛଛͳ͏ 10
11. ܕͷਖ਼͠͞Λଛͳ͏ let a = AnyCollection<String>(["hello"]) let b = AnyCollection<Character>("hello") let c = b[a.startIndex] ࣮ߦ࣌(!)Τϥʔ Collection.Indexʹؔ͢Δܕ৘ใ͕ࣦΘΕ͍ͯ Δ 11
12. ॻ͖ࠐΈ protocol P {} extension Int : P {} struct Container { var value: P { get { return _value } set { _value = newValue as! Int } } var _value: Int = 1 } ࣮࣭తʹsuper typeͳͷͰɺcontravarianceϙδγϣϯͰյ ΕΔ 12
13. ύϑΥʔϚϯεΛଛͳ͏ ϥούʔʹแ·ΕͯΔ෼஗͍ 13
14. ղܾํ๏ 14
15. Opaque Result Type some P ʮϓϩτίϧPΛຬͨ͢ԿΒ͔ͷܕʯΛද͢ه๏ 15
16. ؔ਺ͷฦΓ஋Ͱ࢖͑Δ extension Int : P {} func getP() -> some P { return 3 } 16
17. ϓϩύςΟͰ࢖͑Δ var propertyP: some P { get { ... } set { ... } } 17
18. associated type͕͍ͭͯͯ΋࢖͑Δ func numbers() -> some MutableCollection { return [1, 2, 3] } var xs = numbers() let i0 = xs.startIndex let i1 = xs.index(after: i0) xs[i0] = xs[i1] print(xs) // [2, 2, 3] 18
19. ͕͜͜ϛι 2ͭͷsome P͸ҧ͏ܕ func f1() -> some P func f2() -> some P var a = f1() let b = f2() a = b // ίϯύΠϧΤϥʔ 19
20. ORT͸ؔ਺୯ҐͷΞΠσϯςΟςΟΛ࣋ͭ ԼهͷΑ͏ͳঢ়ଶΛ૝૾͢Δͱྑ͍ struct ResultOfF1 : P {} func f1() -> ResultOfF1 struct ResultOfF2 : P {} func f2() -> ResultOfF2 var a = f1() let b = f2() a = b // ίϯύΠϧΤϥʔ 20
21. ORTͷந৅Խදݱ some Pͱͯ͠ҙຯ෇͚͞ΕΔͨΊɺকདྷͷόʔ δϣϯͰਅͷܕΛมߋͰ͖Δ ιʔεޓ׵ੑ͚ͩͰ͸ͳ͘ɺόΠφϦޓ׵ੑ͕͋ Γɺ࠶ίϯύΠϧͤͣʹมߋͰ͖Δ // ver 1.0.0 func f() -> some P { return 3 } // ver 1.1.0 func f() -> some P { return "3" } 21
22. ໰୊ͷղܾΛΈ͍ͯ͘ • ܕ৘ใͷอ࣋ • ॻ͖ࠐΈ • ύϑΥʔϚϯε 22
23. ܕ৘ใͷอ࣋ func numbers() -> some Collection { return [1, 2, 3] } func message() -> some Collection { return "hello" } let a = numbers() let b = message() let x = a[b.startIndex] // ܕΤϥʔ 23
24. ॻ͖ࠐΈՄೳ struct S { var value: some P { get { return _value } set { _value = newValue as! Int } } var _value: Int = 3 } var s = S() let x = s.value s.value = x // OK s.value = Int(1) // Error s.value = "hello" // Error 24
25. ύϑΥʔϚϯε ίϯύΠϥ͕ਅͷܕΛ஌͍ͬͯΔ࣌͸ɺ࠷దԽʹ ΑΓਅͷܕͱͯ͠ѻ͏ίʔυʹಛघԽ͞ΕΔͨ ΊɺෆཁͳύϑΥʔϚϯεϩε͕ແ͍ 25
26. ʮ࠷దԽͰ͖Δͱ͖͸଎͍ʯͱ͍͏ҙຯͰ͸ Existentialͱಉ͡ɻԿ͕ҧ͏ͷ͔ʁ Existential͸super typeͰ͋ΔͨΊɺʮଞͷܕ͕ ೖ͍ͬͯΔՄೳੑ͕ͳ͍ʯূ໌͕ඞཁɻ ORT͸ʮ஌Βͳ͍͋ΔܕʯͳͷͰɺͦͷূ໌͸ෆ ཁɻ୯ʹͦͷਅͷܕΛ஌Ε͹ྑ͍͚ͩɻ ݁Ռͱͯ͠ಉҰϞδϡʔϧͳΒৗʹ࠷దԽՄೳɻ 26
27. ൃల 27
28. ORTͷಋೖʹ͋ͨͬͯٞ࿦͕֦େ͍ͯͬͨ͠ɻ ऩरΛ͚ͭΔͨΊ৽͍͠ϚχϑΣετ͕࡞ΒΕ ͨɻ Improving the UI of generics https://forums.swift.org/t/improving-the-ui-of- generics/22814 Generic Manifestoʹଓ͘ࢦ਑ 28
29. ORT͸δΣωϦΫεͱࣅ͍ͯΔ // PͰ͋ΔਅͷܕΛฦ͢ func makeSomeP() -> some P // PͰ͋ΔਅͷܕXΛड͚औΔ func useGeneP<X: P>(_ x: X) 29
30. ͜Εͱ͸ҧ͏ // PͰ͋ΔਅͷܕXΛฦ͢ func makeGeneP<X: P>() -> X ͜ͷX͸ݺͼग़͠ଆ͕ܾΊΔ some P͸ݺͼग़͞Εଆ͕ܾΊΔ 30
31. Reverse Generics ݺͼग़͞Εଆ͕ܾΊΔδΣωϦοΫύϥϝʔλͱ ͍͏৽֓೦Λߟ͑ͯΈΔ func makeRevGeneP() -> <X: P> X 31
32. ORT͸Reverse GenericͷsugarͱΈͳͤΔ // PͰ͋ΔਅͷܕΛฦ͢ func makeSomeP() -> some P // PͰ͋ΔਅͷܕXΛฦ͢ func makeRevGeneP() -> <X: P> X 32
33. Reverse GenericsΛ࢖͏ͱɺදݱྗ্͕͕Δ // 2ͭͷsome Pͷؔ࿈Λॻ͚ͳ͍ func makePS() -> (some P, some P) // 2ͭͷʮಉҰͷʯPΛຬͨ͢ܕ func makePS() -> <X: P> (X, X) 33
34. ORTߏจͷ֦ுҊ func makePS() -> (some P A, some P B) where A == B 34
35. Opaque Result Type → Reverse Generics ?? → Generics 35
36. Opaque Argument Type ΋͠someΛҾ਺෦෼ʹॻ͚ͨΒɺGenericsͷ sugarͱΈͳͤΔ // PͰ͋ΔਅͷܕΛड͚औΔ func useSomeP(_ x: some P) // PͰ͋ΔਅͷܕXΛड͚औΔ func useGeneP<X: P>(_ x: X) 36
37. // PͰ͋ΔਅͷܕΛड͚औΔ func useSomeP(_ x: some P) // PͰ͋ΔਅͷܕXΛड͚औΔ func useGeneP<X: P>(_ x: X) ಄ͷதͰҰ౓XΛهԱ͠ͳ͍ͷͰಡΈ΍͍͢ɺྲྀ ߦΓͦ͏ 37
38. ORTͱExistential Α͘ࣅ͍ͯΔ // PΛຬͨ͢**ͱ͋Δ**ܕΛฦ͢ func makeSomeP() -> some P // PΛຬͨ͢**ͲΜͳ**ܕͰ΋୅ೖͰ͖Δ var b: P = ... 38
39. Existentialͷanyه๏ // PΛຬͨ͢**ͱ͋Δ**ܕΛฦ͢ func makeSomeP() -> some P // PΛຬͨ͢**ͲΜͳ**ܕͰ΋୅ೖͰ͖Δ var b: any P ରশతͰ͖Ε͍ 39
40. Protocol੍໿ͱExistentialͷྨࣅ ॳڃऀࡴ͠ // P͸੍໿ func useGeneP<X: P>(_ x: X) // P͸Existential func useAnyP(_ x: P) 40
41. ҧ͏ػೳ͸ҧ͏ه๏ͷ΄͏͕Θ͔Γ΍͍͢ // P͸੍໿ func useGeneP<X: P>(_ x: X) // P͸Existential func useAnyP(_ x: any P) 41