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Mobile Programming Optional
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yuichiro_takahashi
December 19, 2018
Technology
0
140
Mobile Programming Optional
モバイルプログラミングの授業で使うスライドです
yuichiro_takahashi
December 19, 2018
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Transcript
OPTIONAL TYPE MOBILE PROGRAMMING 19TH DEC
OPTIONAL TYPE?
ςΩετ OPTIONAL TYPE? ▸ Swiftʹසൟʹग़ͯ͘Δ ? ! ϚʔΫͷਖ਼ମ ▸
Swift͚ͩͰͳ͘ϞμϯͳݴޠʹΑ͘ݟΒΕΔ nil (null) Λ҆શʹѻ͏ҝͷػೳ ▸ ී௨ͷ͚ͩͰͳ͘ nil ೖΕΔ͜ͱ͕Ͱ͖ΔίϯςφͷΑ͏ͳͷ ▸ ܕఆٛͷࡍʹඌʹ ? Λ͚ͭΔ͜ͱͰOptional Type ʹͳΔ ▸ SwiftͰOptionalͱͯ͠ఆٛ͞ΕͨมͷΈnilΛೖ͢Δ͜ͱ͕Ͱ͖Δ ▸ Optional TypeʹͳΔͱී௨ͷܕͱͯ͑͠ͳ͍ͷͰҰOptional͔Β σʔλΛऔΓग़͢ඞཁ͕͋Δ
ςΩετ ࣮ࡍͷίʔυ // มͷ߹ var indexOrNil: Int? = 0 //
͜ͷΑ͏ʹॻ͚Δ var optionalNum: Optional<Int> = 10 // ؔͷ߹ func getImage(named: String?) -> UIImage? { // লུ ... } // ͜ΕͰ͖ͳ͍ print("added: \(optionalNum + 10)”) // ͳΜΒ͔ͷํ๏ͰOptional͔ΒΛऔΓग़͢ඞཁ͕͋Δ(ࠓճ!ϚʔΫ) print("added: \(optionalNum! + 10)”)
ͳΜΒ͔ͷํ๏ͬ ͯʁ
OPTIONAL UNWRAP ʹ͍ͭͯ
ςΩετ OPTIONAL UNWRAP? ▸ ίʔυͷྫͰݟͨΑ͏ʹOptional typeҰσʔλΛऔΓ ग़͔ͯ͠Β͏ඞཁ͕͋Δ ▸ ͜ΕΛ unwrap(։ࣔ?)
ͱݺͿ ▸ unwrap͢Δํ๏͍͔ͭ͋͘ΔͷͰঢ়گʹΑ͍͚ͬͯ Δ͜ͱ͕େࣄ
ํ๏1. FORCED UNWRAP
ςΩετ FORCED UNWRAP? ▸ ଟ͜Ε͕Ұ൪͓खܰͳํ๏ ▸ optionalͰఆٛ͞Εͨมͷඌʹ ! ϚʔΫΛ͚ͭΔ͚ͩ ▸
͕ͨͩ͋͠Δ͔nil͔Ͱ͋Δ͔ʹؔΘΒͣڧ੍తʹOptionalΛ unwrapͯ͠͠·͏ ▸ ͦͷҝnilͩͬͨ߹ϓϩάϥϜ͕Ϋϥογϡ͢Δ ▸ ͲΜͳͱ͖͕࣮֬ʹೖ͍ͬͯΔͱ͍͏͜ͱ(ઈରnilʹͳΒͳ͍ ͱ͍͏ࣄ)͕อূͰ͖Δ߹ͷΈ͍·͠ΐ͏
ςΩετ ࣮ࡍͷίʔυ // มͷ߹ var nilNumber: Int? = nil //
͜ͷΑ͏ʹॻ͚Δ var optionalNum: Optional<Int> = 10 //ม optionalNum ͷඌʹ!ϚʔΫΛ͚ͭͯΛऔΓग़͢ print("added: \(optionalNum! + 10)”) //͜ΕΫϥογϡʂ print("added: \(nilNumber! + 10)”)
ํ๏2. NIL COALESCING OPERATOR
ςΩετ NIL COALESCING OPERATOR? ▸ ͪ͜Βඇৗʹ͓खܰͳํ๏͔ͭ҆શ ▸ optionalͰఆٛ͞ΕͨมͷޙΖʹ ?? <defaultValue>
Λͬͭ͘ ͚Δ ▸ ?? ԋࢉࢠ͕͋ΕͦͷΛฦ͠ɺnilͰ͋Εࢦఆͨ͠ defaultValueΛฦ͢ ▸ defaultValue ͑͞༻ҙͰ͖Ε҆શ͔͓ͭखܰʹ Unwrap Ͱ͖Δ ▸ get or elseͱݺΕΔ͜ͱ͋Δ
ςΩετ ࣮ࡍͷίʔυ // มͷ߹ var nilNumber: Int? = nil //
͜ͷΑ͏ʹॻ͚Δ var optionalNum: Optional<Int> = 10 // ม optionalNum ͷޙΖʹ ?? ϚʔΫΛ͚ͭͯΛऔΓग़͢ // ม optionalNum ͕ nil ͩͬͨΒ 0 ʹͳΔ print("added: \((optionalNum ?? 0) + 10)”)
ํ๏3.OPTIONAL BINDING
ςΩετ OPTIONAL BINDING? ▸ ԋࢉࢠΛ͏ํ๏ʹൺΔͱίʔυྔ૿͑Δ͕ͱͯ҆શ ʹѻ͑Δ ▸ if let
guard let, switch Λͬͯ unwrap ͢Δํ๏ ▸ ͦΕͧΕܗҧ͏͕શͯ optional ͷதΛ৽͍͠ఆʹଋ റ(bind)͢Δ͜ͱͰunwrap͢Δ ▸ Ұ൪Α͘͏ํ๏͔
ςΩετ ࣮ࡍͷίʔυ * ͘ͳΔͷͰXcodeͰ