Option Type

Swift Option Type pitfalls

Transcript

1. 0QUJPO
   5ZQF !XBHZV
2. ࠓ೔ͷϙΠϯτ w ओʹ
   4XJGU
   ͷ࿩͠·͢
   w ࠷ۙͷ
   /VMM
   ͕୅ೖͰ͖ͳ͍ϓϩάϥϛϯάݴޠ͕૿͑ͯΔ
   w )BTLFMM
   4DBMB
   '
   3VTU
   4XJGU
   ,PUMJO
   FUD
   w ࣮ݱ͢Δ࢓૊ΈͷҰ͕ͭ
   0QUJPO
   5ZQF
   w ʢ4XJGU
   Ͱ͸
   0QUJPOBMɺ,PUMJO
   Ͱ͸
   /VMMBCMF
   ͱݴ͍·͢ʣ
   w ࠷ۙͷྲྀߦΓͳͷͰ
   +BWB4DSJQU
   ͱ͔ʹ΋͖͡ʹೖΔ͔΋
   w ϥΠϒϥϦϕʔεͩͱ
   OPEFPQUJPOT
   ͱ͔͋ΔΜ͚ͩͲݴޠαϙʔτ͕ͳ͍ ͱ͠ΜͲ͍
   w ࢖ͬͯΈΔͱͪΐ͍ͪΐ͍τϥοϓ͕͋ΔͷͰͦͷลΛڞ༗
3. CJMMJPOEPMMBS
   NJTUBLF w *
   DBMM
   JU
   NZ
   CJMMJPOEPMMBS
   NJTUBLF
   *U
   XBT
   UIF
   JOWFOUJPO
   PG
   UIF
   OVMM
   SFGFSFODF
   JO
   
   "U
   UIBU
   UJNF
   *
   XBT
   EFTJHOJOH
   UIF
   pSTU
   DPNQSFIFOTJWF
   UZQF
   TZTUFN
   GPS
   SFGFSFODFT
   JO
   BO
   PCKFDU
   PSJFOUFE
   MBOHVBHF
   "-(0-
   8 
   .Z
   HPBM
   XBT
   UP
   FOTVSF
   UIBU
   BMM
   VTF
   PG
   SFGFSFODFT
   TIPVME
   CF
   BCTPMVUFMZ
   TBGF
   XJUI
   DIFDLJOH
   QFSGPSNFE
   BVUPNBUJDBMMZ
   CZ
   UIF
   DPNQJMFS
   #VU
   *
   DPVMEOU
   SFTJTU
   UIF
   UFNQUBUJPO
   UP
   QVU
   JO
   B
   OVMM
   SFGFSFODF
   TJNQMZ
   CFDBVTF
   JU
   XBT
   TP
   FBTZ
   UP
   JNQMFNFOU
   5IJT
   IBT
   MFE
   UP
   JOOVNFSBCMF
   FSSPST
   WVMOFSBCJMJUJFT
   BOE
   TZTUFN
   DSBTIFT
   XIJDI
   IBWF
   QSPCBCMZ
   DBVTFE
   B
   CJMMJPO
   EPMMBST
   PG
   QBJO
   BOE
   EBNBHF
   JO
   UIF
   MBTU
   GPSUZ
   ZFBST
   w ͦΕ͸ԯυϧʹ΋૬౰͢ΔࢲͷޡΓͩɻOVMMࢀরΛൃ໌ͨ͠ͷ͸೥ͷ͜ͱͩͬͨɻ౰࣌ɺ ࢲ͸ΦϒδΣΫτࢦ޲ݴޠ
   "-(0-
   8
   ʹ͓͚ΔࢀরͷͨΊͷแׅతܕγεςϜΛઃܭ͍ͯͨ͠ɻ ໨ඪ͸ɺίϯύΠϥͰͷࣗಈνΣοΫͰશͯͷࢀর͕׬શʹ҆શͰ͋Δ͜ͱΛอূ͢Δ͜ͱͩͬ ͨɻ͔͠͠ɺࢲ͸୯ʹͦΕ͕༰қͩͱ͍͏͚ͩͰɺແޮͳࢀরΛؚΊΔ༠࿭ʹ఍߅Ͱ͖ͳ͔ͬͨɻ ͜Ε͸ɺޙʹ਺͑੾Εͳ͍աͪɺ੬ऑੑɺγεςϜΫϥογϡΛҾ͖ى͜͠ɺաڈ೥ؒͰ ԯυϧ૬౰ͷۤ௧ͱଛ֐ΛҾ͖ىͨ͜͠ͱΈΒΕΔɻ
   w IUUQXXXJOGPRDPNQSFTFOUBUJPOT/VMM3FGFSFODFT5IF#JMMJPO%PMMBS.JTUBLF5POZ )PBSF
4. 4XJGU w 4XJGU
   JT
   B
   HFOFSBMQVSQPTF
   QSPHSBNNJOH
   MBOHVBHF
   CVJMU
   VTJOH
   B
   NPEFSO
   BQQSPBDI
   UP
   TBGFUZ
   QFSGPSNBODF
   BOE
   TPGUXBSF
   EFTJHO
   QBUUFSOT
   w IUUQTTXJGUPSHBCPVU
5. ҎԼɺ4XJGUͷσϞΛ ަ͑ͳ͕Βߦ͖·͢
6. /VMM
   FSSPS w 4XJGU
   ͷී௨
   OPOPQUJPOBM
   ͷม਺͸
   /VMM
   ඇڐ༰Ͱ͢
   w 4XJGU
   Ͱ͸
   OJM
   ͕
   /VMM
   Ͱ͢
   w OJM
   Λม਺ʹ୅ೖ͢ΔͱΤϥʔʹͳΓ·͢
   w ద౰ʹ
   4XJGU
   ৮Δͱଟ෼࠷ॳʹૺ۰͢ΔίϯύΠϥΤϥʔ
   w Α͘෼͔ͬͯͳ͍ͱ௒ΠϥΠϥ͢Δ
   w 4XJGU
   ݴޠʹ૊Έࠐ·Ε͍ͯΔػೳͰ͢
7. /VMM
   FSSPS WBS
   TUS
   4USJOH
   
   OJM
8. ॳظԽ w ม਺͸ඇ
   OJM
   ஋ͰॳظԽ͠·͢
   w ʢͪͳΈʹ
   4XJGU
   Ͱ͸
   WBS
   ͕
   WBSJBCMFɺMFU
   ͕
   DPOTUBOU
   ͳͷͰ͕͢ɺҰൠతͳม਺ʗఆ਺ͱ؆୯ ʹଊ͑Δͱ৭ʑ΍΍͍͜͠࿩͕͋Γ·͢ͷͰɺWBS
   
   MFU
   Λ۠ผͤͣม਺ͱදه͍ͯ͠·͢ʣ
9. ॳظԽ WBS
   TUS
   4USJOH
   
   l999z
10. 0QUJPOBM w OJM
    ͰॳظԽ͍ͨ͠৔߹͸
    0QUJPOBM
    ܕม਺Λ࢖༻ ͠·͢
    w ܕͷޙΖʹ
    
    Λ෇͚Δͱ
    0QUJPOBM
    ܕม਺ʹͳΓ· ͢
11. 0QUJPOBM WBS
    TUS
    4USJOH
    
    OJM
    QSJOU TUS
12. 0QUJPOBM w ඇ
    0QUJPOBM
    ܕม਺ʹ
    0QUJPOBM
    ܕม਺Λ୅ೖ͢Δ ͜ͱ͸Ͱ͖·ͤΜ
    w 4XJGU
    Λ࢖ͬͯద౰ʹίʔσΟϯά͢Δͱଟ෼࠷ॳ ʹૺ۰͢Δҙຯෆ໌ͳίϯύΠϥΤϥʔ
13. 0QUJPOBM GVOD
    G TUS
    4USJOH
    \
    
    
    
    
    QSJOU TUS
    ^
    WBS
    TUS
    4USJOH
    
    OJM
    G TUS
14. 6OXSBQ w 0QUJPOBM
    ܕม਺͔Βඇ
    0QUJPOBM
    ܕͷ஋ΛऔΓग़ ͢͜ͱΛ
    4XJGU
    Ͱ͸
    6OXSBQ
    ͱݺͼ·͢ɻ
    w 6OXSBQ
    ͢Δʹ͸
    0QUJPOBM
    ܕม਺ͷޙΖʹ
    
    Λ෇ ͚·͢ɻ
15. 6OXSBQ GVOD
    G TUS
    4USJOH
    \
    
    
    
    
    QSJOU TUS
    ^
    WBS
    TUS
    4USJOH
    
    """
    G TUS
16. 0QUJPOBM
    $IBJOJOH w 0QUJPOBM
    ܕม਺ͷϝϯό
    1SPQFSUZ
    
    NFUIPE
    ʹ ҆શʹΞΫηε͢Δํ๏Ͱ͢ɻ
    w 0QUJPOBM
    ม਺ͷޙΖʹ
    
    Λ෇͚ͯϝϯόʹΞΫη ε͢ΔͱɺOJM
    
    ඇ
    OJM
    ໰ΘͣϝϯόʹΞΫηεͰ͖ ·͢ɻ
17. 0QUJPOBM
    $IBJOJOH DMBTT
    5
    \
    
    
    
    
    WBS
    TUS
    4USJOH
    
    999
    ^
    WBS
    U
    5
    
    5
    WBS
    TUS
    
    U TUS
    QSJOU TUS
    U
    
    OJM
    TUS
    
    U TUS
    QSJOU TUS
18. 0QUJPOBM
    $IBJOJOH w 0QUJPOBM
    $IBJOJOH
    ͕ฦ͢஋͸
    0QUJPOBM
    ܕʹͳΓ ·͢
    w 0QUJPOBM
    $IBJOJOH
    Ͱऔಘͨ͠஋Λඇ
    0QUJPOBM
    ܕ ม਺΍ඇ
    0QUJPOBM
    ܕҾ਺Λड͚औΔؔ਺ʹ౉ͦ͏ ͱ͢ΔͱίϯύΠϧΤϥʔ͕ൃੜ͠·͢
    w 4XJGU
    ͕෼͔͖ͬͯͨͱࢥ͏͜Ζʹૺ۰͢Δͱࢥ ͍·͢
19. 0QUJPOBM
    $IBJOJOH DMBTT
    5
    \
    
    
    
    
    WBS
    TUS
    4USJOH
    
    999
    ^
    GVOD
    G T
    4USJOH
    \
    
    
    
    
    QSJOU T
    ^
    WBS
    U
    5
    
    5
    G U TUS
20. 0QUJPOBM
    $IBJOJOH w ༨ஊͰ͕͢
    w
    ͸͋͘·Ͱ΋
    0QUJPOBM
    $IBJOJOH
    ͳͷͰ຤ඌ ʹ෇͚Ε·ͤΜ
    w $P⒎FF4DSJQU
    ॻ͍ͯΔͱΑ͘෼͔Βͳ͘ͳΔ
    w 
    ͸
    6OXSBQ
    ͳͷ෇͚Ε·͢
21. 0QUJPOBM
    $IBJOJOH DMBTT
    5
    \
    
    
    
    
    WBS
    T
    4USJOH
    
    99
    ^
    WBS
    D
    
    5
    WBS
    T
    
    DT
    WBS
    U
    
    DT
22. JG
    MFU
    
    HVBSE
    FMTF w 0QUJPOBM
    ܕͷม਺΍
    0QUJPOBM
    $IBJOJOH
    ͨ͠஋ʹ ҆શʹΞΫηε͍ͨ͠৔߹͸
    JG
    MFU
    ͔
    HVBSE
    FMTF
    ߏจ͕ศརͰ͢
23. JG
    MFU DMBTT
    5
    \
    
    
    
    
    WBS
    TUS
    4USJOH
    
    999
    ^
    GVOD
    G T
    4USJOH
    \
    
    
    
    
    QSJOU T
    ^
    WBS
    U
    5
    
    5
    JG
    MFU
    T
    
    U TUS
    \
    
    
    
    
    G T
    ^
24. HVBSE
    FMTF GVOD
    G T
    4USJOH
    \
    
    
    
    
    HVBSE
    MFU
    U
    
    T
    FMTF
    \
    
    
    
    
    
    
    
    
    SFUVSO
    
    
    
    
    ^
    
    
    
    
    QSJOU U
    ^
    G OJM
    
25. *NQMJDJUMZ
    6OXSBQQFE
    0QUJPOBM w *NQMJDJUMZ
    
    ҉໧త
    w 
    ͱ͔
    
    Λॻ͔ͳͯ͘΋ɺ҉໧తʹ
    6OXSBQ
    ͞Ε Δ
    0QUJPOBM
    ܕͷ͜ͱͰ͢
26. *NQMJDJUMZ
    6OXSBQQFE
    0QUJPOBM WBS
    T
    4USJOH
    
    OJM
    JG
    T
    
    OJM
    \
    
    
    
    
    QSJOU T
    ^
27. NPOBE w 0QUJPOBM
    ܕʹ͸
    NBQ
    ͱ
    qBU.BQ
    ͱ͍͏ϝιου ͕ఆٛ͞Ε͍ͯ·͢ɻ
    w NBQ
    ͸
    0QUJPOBM
    ܕม਺͕ඇ
    OJM
    Λ࣋ͭ৔߹ʹؔ਺ Λద༻͠
    0QUJPOBM
    ܕͰฦ͠·͢ɻ
    w qBU.BQ
    ͸0QUJPOBM
    ܕม਺͕ඇ
    OJM
    Λ࣋ͭ৔߹ʹ ؔ਺Λద༻͠ඇ
    0QUJPOBM
    ܕͰฦ͠·͢ɻ
    
28. NPOBE WBS
    T
    4USJOH
    
    999
    WBS
    U
    
    TNBQ
    \
    
    
    
    
    
    
    """
    ^
    QSJOU U
    U
    
    TqBU.BQ
    \
    
    
    
    
    
    
    """
    ^
    QSJOU U
    WBS
    V
    
    TNBQ
    \
    
    
    
    
    0QUJPOBM4USJOH 
    
    """
    ^
    QSJOU V
    U
    
    TqBU.BQ
    \
    
    
    
    
    0QUJPOBM4USJOH 
    
    """
    ^
    QSJOU U
29. ࣮૷໘ͷ࿩ w 0QUJPOBM
    
    *NQMJDJUMZ
    6OXSBQQFE
    0QUJPOBM
    ܕม ਺͸
    (FOFSJD
    Ͱ࣮૷͞Ε͍ͯ·͢
    w
    ΍
    
    Λ࢖Θͣ
    (FOFSJD
    ߏจͰม਺ఆٛ͢Δ͜ ͱ΋ՄೳͰ͢
    w 4XJGU
    ʹݶΒͣଞͷݴޠ΋ࣅ༷ͨͳײ͡Ͱ͢
    
30. ࣮૷໘ͷ࿩ WBS
    T
    0QUJPOBM4USJOH
    
    """
    WBS
    U
    *NQMJDJUMZ6OXSBQQFE0QUJPOBM4USJOH
    
    """
31. ϓϩάϥϛϯάαϙʔτ w ͜ͷลͰ
    OJM
    ॳظԽΤϥʔͱ͔ग़ͯ͠·͢
    w IUUQTHJUIVCDPNBQQMFTXJGUCMPCNBTUFS JODMVEFTXJGU"45 %JBHOPTUJDT4FNBEFG--
    w IUUQTHJUIVCDPNBQQMFTXJGUCMPCNBTUFS MJC4FNB$4%JBHDQQ-
32. 0QUJPO
    5ZQF
    ͷఆٛ w 0QUJPO
    5ZQF
    ͸
    /POF
    ͔
    4PNF WBMVF
    Λฦ͢
    5BHHFE
    6OJPO
    λά෇͖ڞ༻ମ
    Ͱ͢ return: A ! A? = a 7! Just a bind: A? ! ( A ! B? ) ! B? = a 7! f 7! ( Nothing if a = Nothing f a0 if a = Just a0
33. ͓ΘΓ