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ܧଓ͠ͱܖʹΑΔઃܭ
Continuation-Passing Style and Design By Contract
by.
2019/3/19 try! Swift Pre Talks 2019
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takasek
@takasek
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ʮίϯύΠϧΤϥʔϥϯλΠϜΤϥʔΛ͍ͯ͘͠
͚ͩͰiOSΞϓϦͷ࡞Γํ͕Θ͔ΔϓϩδΣΫτʯ
ʮ͓લΒ͕ModelͱݺͿΞϨΛͳΜͱݺͿ͖͔ʯ
ʮiOSΞϓϦઃܭύλʔϯೖʯʢڞஶʣ
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ʮiOSΞϓϦઃܭύλʔϯೖʯ
ධൃചதʂ
https://peaks.cc/takasek/iOS_architecture
takasek୲ষ
ୈ1ষʮઃܭ͢Δͱ͍͏͜ͱʯ
ୈ2ষʮઃܭʹύλʔϯΛద༻͢Δલʹʯ
ୈ3ষʮSwiftΒ͘͠ઃܭ͢Δʯ
ୈ4ষʮΞʔΩςΫνϟͷύλʔϯΛௗᛌ͢
Δʯ
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ܧଓ͠
Continuation-
Passing Style(CPS)
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// Without CPS
func doSomething(i: Int) -> String {
sleep(100)
return "\(i)"
}
// With CPS
func doSomething(i: Int, completion: @escaping (String) -> Void) {
DispatchQueue.global().async {
sleep(100)
completion("\(i)")
}
}
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!
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func doSomething(
i: Int,
completion: @escaping (String) -> Void
)
͜ͷΠϯλϑΣʔεʹɺخ͘͠ͳ͍͕͋Γ·͢
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ʮ͋ͬɺಡΊͨʯ
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ʮίʔϧόοΫࠈͷͰ͠ΐʯ
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ҧ͍·͢
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ܖʹΑΔ
ઃܭ
Design By Contract
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ܖʹΑΔઃܭ
Design By Contract
ΦϒδΣΫτࢦΛΊͨݚڀऀ
όʔτϥϯυɾϝΠϠʔʹΑΔɺ
৴པੑͷߴ͍γεςϜΛ
ߏங͢ΔͨΊͷΞΠσΞ
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ܖʹΑΔઃܭ
͋Δϧʔνϯ͕ɺݺΕΔ૬खͱͷؒͰऔΓަΘܾ͢Ί͝ͱΛʮද໌ʯ͢Δ
• ࣄલ݅ɿ
ݺͿଆ͕͜ͷ݅Λอূ͢Δ߹ͷΈɺϧʔνϯॲཧΛਖ਼͘͠ߦ͏
ҾͷܕͳͲͰදݱՄೳ
• ࣄޙ݅ɿ
ࣄલ͕݅कΒΕ͍ͯͨΒɺϧʔνϯͷ࣮ߦ݁Ռ͕อূ͢Δ݅
ΓͷܕͳͲͰදݱՄೳ
ࣄલ͕݅ഁΒΕɺࣄޙ݅ΛकΕͳ͍߹ྫ֎͕ൃੜ͢Δ
• ෆม݅ ʹ͍ͭͯࠓճলུ
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ίʔυͱද໌ͷ۩ମྫ
func half(of i: Int) throws -> Int {
assert(i.isMultiple(of: 2))
if !i.isMultiple(of: 2) { throw Error.isOdd }
return i / 2
}
• ࣄલ݅:
• Int ͔͠ड͚͚ͭ·ͤΜ
• ۮ͔͠ड͚͚ͭ·ͤΜ (ܕͱͯ͠දݱෆೳ)
• ࣄޙ݅: ඞͣ Int Λฦ͠·͢
• ྫ֎: ۮͰͳ͔ͬͨ߹ྫ֎Λ͛·͢
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ʮܖʹΑΔઃܭʯͷ࣮ݱͷͨΊʹɺSwiftͷܕ͚େཱ͖͍ͬͯ͘Δ
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ͯ͞
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func half(of i: Int) throws -> Int {
if !i.isMultiple(of: 2) {
throw Error.isOdd
}
return i / 2
}
͜ΕΛCPSʹมͯ͠Έ·͠ΐ͏
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func half(of i: Int, completion: (Int) -> Void) {
if !i.isMultiple(of: 2) {
return
}
completion(i / 2)
}
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OK, حͷ߹
֬ೝ͠Α͏ʂ
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ݺΕͳ͍…ʁ
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completionͷ
ݺͼ࿙Ε
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func half(of i: Int, completion: (Int) -> Void) {
if !i.isMultiple(of: 2) {
return //
!
}
completion(i / 2)
}
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enum Result {
case success(T)
case error(Error)
}
func half(of i: Int, completion: (Result) -> Void) {
if !i.isMultiple(of: 2) {
return //
!
}
completion(.success(i / 2))
}
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enum Result {
case success(T)
case error(Error)
}
func half(of i: Int, completion: (Result) -> Void) {
if !i.isMultiple(of: 2) {
completion(.error(.isOdd)) //
}
completion(.success(i / 2))
}
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ͬͨʂ
͏ҰڍಈΛ
֬ೝ͠Α͏ʂ
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2ݺΕ͍ͯΔ
…ͩͱ…ʁ
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func half(of i: Int, completion: (Result) -> Void) {
if !i.isMultiple(of: 2) {
completion(.error(.isOdd))
//
!
}
completion(.success(i / 2))
}
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func half(of i: Int, completion: (Result) -> Void) {
if !i.isMultiple(of: 2) {
completion(.error(.isOdd))
return //
!
}
completion(.success(i / 2))
}
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ܧଓ͠ελΠϧΛ͏ͱ
੩తܕ͚ͷԸܙΛ
ड͚ΒΕͳ͍
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ͳͥͳͷ͔
ΓͷܕʹΑͬͯ
ࣄޙ݅ΛදݱͰ͖ͳ͍͔Β
(T, (U) -> Void) -> Void
Void࠷ऑͷࣄޙ݅
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Ͳ͏͢Ε͍͍͔
ΓͷܕʹΑͬͯ
ࣄޙ݅Λදݱ͢Ε͍͍
(T) -> XXX
ʮ͍ͣΕ݁Ռ͕ಘΒΕΔʯ͜ͱΛܕ͚ͰࣔͤΕɺ
ඇಉظॲཧͰΓΛػೳͤ͞ΒΕΔ
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func half(of i: Int) -> RxSwift.Single {
if !i.isMultiple(of: 2) {
return .error(Error.isOdd)
}
return .just(i / 2)
}
͜ΕͳΒ੩తܕ͚ͷԸܙΛड͚ͭͭɺ
ʮඇಉظͰ͋Δ͜ͱʯΛදݱͰ͖Δ
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• Promise(Future) ύλʔϯ
• PromiseK
• Hydra
• RxSwift
• etc
• async/await
• comming soon in Swift 5.x!?
• ͜ͷݴޠ༷Λϕʔεʹ Future ܕΛߏஙՄೳ
CPSΛશ໘తʹஔ͖͔͑Մೳ͔ͱ͍͏ͱ͍͕͠ɺ
બࢶΛͬͨ͏͑ͰύλʔϯΛબͼ͍ͨ
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݁
ɾਓؒϛεΛ͠·͢
ɾϛεΛ͢Δલʹɺ
ද໌ΛίϯύΠϥ͕͔ΔܗͰॻ͚ͳ͍͔
ҙࣝ͠ͳ͕Βઃܭ͠·͠ΐ͏
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͓·͚
ͱͯ5ͰޠΓ͖Εͳ͍
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ʮද໌ʯʹ͍ͭͯͷิ
• ҾɾΓͷܕ͚͕ͩද໌Ͱͳ͍ͱݴ͚ͬͨΕͲ…
• assert ͚ͩͰͳ͘ɺSwiftͰݴ͑ generics conditional conformanceද໌ͷํ๏
• ͭʹɺίϯύΠϥղऍෆೳͳද໌ྑ͘ͳ͍…Θ͚Ͱͳ͍
• දݱྗΛ্͛Δͱֶशίετɾෳࡶੑ͕ϖΠ͠ͳ͍͜ͱଟ͍ͷͰɺͦ͜όϥϯε
• ͨͱ͑ɺڽͬͨprotocolͷwhere۟ɺৗਓʹཧղग़དྷΔ͔ͬͯݴΘΕΔͱݫ͍͠ΑͶ…
ɹ
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ิͷิ
ٯʹݴ͑ɺ
ܖʹΑΔઃܭ
ݴޠΛΘͣద༻Մೳͳ֓೦Ͱ͢
t_wada͞ΜʹΑΔ
͋͑ͯPHPΛϕʔεʹͨ͠εϥΠυ
PHPer͡Όͳͯ͘ΦεεϝͰ͢
https://speakerdeck.com/twada/php-
conference-2016
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ʮܧଓ͠ʯʹ͍ͭͯͷิ
• ࣮ async/awaitʮ෦తͳCPSมʯͦͷͷͱ͍͑·͢
Continuation Passing Style Revisited
– Fabulous Adventures In Coding
https://blogs.msdn.microsoft.com/ericlippert/2010/10/21/
continuation-passing-style-revisited-part-one/
ͦͷ༁
matarillo.com: ܧଓ͠ελΠϧ(CPS)ͱඇಉظߏจ(async/await)
https://matarillo.com/general/cps
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Swiftͷ async/await ͱ
ܧଓͱ Future ͷؔ
Chris Lattnerͷproposal2ʹΑΔͱɺ
• ଞͷݴޠͰ Future ͕·ͣ͋ͬͯɺͦͷ্ʹasync/await͕͔͍ͬͬͯΔ
• Swiftͷasync/awaitͷઃܭͰͦΕΛલఏͱͤͣɺܧଓΛͦͷ··ѻ͏खஈΛ࿐ग़͍ͤͯ͞
Δ
• ͱ͍͑ Future ͱ͍͏ܕ͚͞Εͨঢ়ଶͰѻ͏ΠϯλϑΣʔεߏஙՄೳͰ͢Αɺͱ͍͏͜ͱ
2 https://gist.github.com/lattner/429b9070918248274f25b714dcfc7619
yimajo͞Μͷʮasync/awaitݚڀಡຊʯ͋ΘͤͯͲ͏ͧ
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ؔ࿈ɿʮܖʹΑΔઃ
ܭʯΛΩʔϫʔυͰ֦
ு͢Δ
ʮܖʹΑΔઃܭʯʹ͍ͭͯৄղ͞Ε
͍ͯΔʮΦϒδΣΫτࢦೖʯʹ
ɺ
ඇಉظʢฒߦʣॲཧΛͱʹ֦ுͨ͠
߹ͷܖͷϙϦγʔʹ͍ͭͯͷٞ
͋Γ·͢
໘ന͍Αʂ
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