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

Transcript

1. OPTIONAL TYPE
   MOBILE PROGRAMMING 19TH DEC
   

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2. OPTIONAL TYPE?
   

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3. ςΩετ
   OPTIONAL TYPE?
   ▸ Swiftʹසൟʹग़ͯ͘Δ ? ΍ ! ϚʔΫͷਖ਼ମ
   ▸ Swift͚ͩͰͳ͘ϞμϯͳݴޠʹΑ͘ݟΒΕΔ nil (null) Λ҆શʹѻ͏ҝͷػೳ
   ▸ ී௨ͷ஋͚ͩͰͳ͘ nil ΋ೖΕΔ͜ͱ͕Ͱ͖ΔίϯςφͷΑ͏ͳ΋ͷ
   ▸ ܕఆٛͷࡍʹ຤ඌʹ ? Λ͚ͭΔ͜ͱͰOptional Type ʹͳΔ
   ▸ SwiftͰ͸Optionalͱͯ͠ఆٛ͞Εͨม਺ͷΈnilΛ୅ೖ͢Δ͜ͱ͕Ͱ͖Δ
   ▸ Optional TypeʹͳΔͱී௨ͷܕͱͯ͠͸࢖͑ͳ͍ͷͰҰ౓Optional͔Β
   σʔλΛऔΓग़͢ඞཁ͕͋Δ
   

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4. ςΩετ
   ࣮ࡍͷίʔυ
   // ม਺ͷ৔߹
   var indexOrNil: Int? = 0
   // ͜ͷΑ͏ʹ΋ॻ͚Δ
   var optionalNum: Optional = 10
   // ؔ਺ͷ৔߹
   func getImage(named: String?) -> UIImage? {
   // লུ ...
   }
   // ͜Ε͸Ͱ͖ͳ͍
   print("added: \(optionalNum + 10)”)
   // ͳΜΒ͔ͷํ๏ͰOptional͔Β஋ΛऔΓग़͢ඞཁ͕͋Δ(ࠓճ͸!ϚʔΫ)
   print("added: \(optionalNum! + 10)”)
   

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5. ͳΜΒ͔ͷํ๏ͬ
   ͯʁ
   

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6. OPTIONAL UNWRAP
   ʹ͍ͭͯ
   

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7. ςΩετ
   OPTIONAL UNWRAP?
   ▸ ίʔυͷྫͰݟͨΑ͏ʹOptional type͸Ұ౓σʔλΛऔΓ
   ग़͔ͯ͠Β࢖͏ඞཁ͕͋Δ
   ▸ ͜ΕΛ unwrap(։ࣔ?) ͱݺͿ
   ▸ unwrap͢Δํ๏͸͍͔ͭ͋͘ΔͷͰঢ়گʹΑͬͯ࢖͍෼͚
   Δ͜ͱ͕େࣄ
   

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8. ํ๏1. FORCED
   UNWRAP
   

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9. ςΩετ
   FORCED UNWRAP?
   ▸ ଟ෼͜Ε͕Ұ൪͓खܰͳํ๏
   ▸ optionalͰఆٛ͞Εͨม਺ͷ຤ඌʹ ! ϚʔΫΛ͚ͭΔ͚ͩ
   ▸ ͨͩ͠஋͕͋Δ͔nil͔Ͱ͋Δ͔ʹؔΘΒͣڧ੍తʹOptionalΛ
   unwrapͯ͠͠·͏
   ▸ ͦͷҝnilͩͬͨ৔߹͸ϓϩάϥϜ͕Ϋϥογϡ͢Δ
   ▸ ͲΜͳͱ͖΋஋͕࣮֬ʹೖ͍ͬͯΔͱ͍͏͜ͱ(ઈରnilʹ͸ͳΒͳ͍
   ͱ͍͏ࣄ)͕อূͰ͖Δ৔߹ͷΈ࢖͍·͠ΐ͏
   

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10. ςΩετ
    ࣮ࡍͷίʔυ
    // ม਺ͷ৔߹
    var nilNumber: Int? = nil
    // ͜ͷΑ͏ʹ΋ॻ͚Δ
    var optionalNum: Optional = 10
    //ม਺ optionalNum ͷ຤ඌʹ!ϚʔΫΛ͚ͭͯ஋ΛऔΓग़͢
    print("added: \(optionalNum! + 10)”)
    //͜Ε͸Ϋϥογϡʂ
    print("added: \(nilNumber! + 10)”)
    

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11. ํ๏2. NIL
    COALESCING OPERATOR
    

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12. ςΩετ
    NIL COALESCING OPERATOR?
    ▸ ͪ͜Β΋ඇৗʹ͓खܰͳํ๏͔ͭ҆શ
    ▸ optionalͰఆٛ͞Εͨม਺ͷޙΖʹ ?? Λͬͭ͘
    ͚Δ
    ▸ ?? ԋࢉࢠ͸஋͕͋Ε͹ͦͷ஋Λฦ͠ɺnilͰ͋Ε͹ࢦఆͨ͠
    defaultValueΛฦ͢
    ▸ defaultValue ͑͞༻ҙͰ͖Ε͹҆શ͔͓ͭखܰʹ Unwrap Ͱ͖Δ
    ▸ get or elseͱݺ͹ΕΔ͜ͱ΋͋Δ
    

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13. ςΩετ
    ࣮ࡍͷίʔυ
    // ม਺ͷ৔߹
    var nilNumber: Int? = nil
    // ͜ͷΑ͏ʹ΋ॻ͚Δ
    var optionalNum: Optional = 10
    // ม਺ optionalNum ͷޙΖʹ ?? ϚʔΫΛ͚ͭͯ஋ΛऔΓग़͢
    // ม਺ optionalNum ͕ nil ͩͬͨΒ 0 ʹͳΔ
    print("added: \((optionalNum ?? 0) + 10)”)
    

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14. ํ๏3.OPTIONAL
    BINDING
    

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15. ςΩετ
    OPTIONAL BINDING?
    ▸ ԋࢉࢠΛ࢖͏ํ๏ʹൺ΂Δͱίʔυྔ͸૿͑Δ͕ͱͯ΋҆શ
    ʹѻ͑Δ
    ▸ if let ΍ guard let, switch Λ࢖ͬͯ unwrap ͢Δํ๏
    ▸ ͦΕͧΕܗ͸ҧ͏͕શͯ optional ͷத਎Λ৽͍͠ఆ਺ʹଋ
    റ(bind)͢Δ͜ͱͰunwrap͢Δ
    ▸ Ұ൪Α͘࢖͏ํ๏͔΋
    

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16. ςΩετ
    ࣮ࡍͷίʔυ
    * ௕͘ͳΔͷͰXcodeͰ
    

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