いいから `!` を使え！ / Shut up and use `!` !

Transcript

1. ͍͍͔Β
   !
   Λ࢖͑ʂ f o r
   : 6 . & .

   *  T X J G U
     

2. } var employedBy = "YUMEMI Inc." var job = "iOS

   Tech Lead" var favoriteLanguage = "Swift" var twitter = "@lovee" var qiita = "lovee" var github = "el-hoshino" var additionalInfo = """ อޢͨ͠ೣ͕ͷൃ৘ظʹಥೖͯ݁͠ߏେม """ final class Me: Developable, Talkable {

3. 4XJGU
   Ͱ
   !
   ࢖ͬͯ·͢ʁ

4. ΋ͪΖΜ
   Bool
   ൓సҎ֎Ͱ

5. 4XJGU
   ʹ͓͚Δ
   !
   ͷओͳ࢖͍ಓ˞ w Optional
   ͷڧ੍
   6OXSBQʢ*60
   ؚΉʣ
   w ܕม׵ͷڧ੍μ΢ϯΩϟετ
   as! w ྫ֎ॲཧͷڧ੍ྫ֎ແࢹ
   try! ˞
   #PPM
   ൓సҎ֎

6. ڞ௨఺ɿϓϩάϥϜ͕ 
 Ϋϥογϡ͢ΔϦεΫ͕͋Δ

7. !
   Λ࢖Θͳ͍ํ͕҆શ 本当にそうか？

8. ͜ͷίʔυͬͯɺ҆શʁ func doSomething() { let image = UIImage(named: "ImageName") ??

   UIImage() // do something with image }

9. ͜ͷίʔυͬͯɺ҆શʁ func doSomething() { guard let appDelegate = UIApplication .shared.delegate

   as? AppDelegate else { return } // do something with appDelegate }

10. ͜ͷίʔυͬͯɺ҆શʁ func doSomething(with data: Data) { do { let decoder

    = JSONDecoder() let response = try decoder.decode(Response.self, from: data) // do something with response } catch { debugPrint(error) return } }

11. ΞϓϦ͕Ϋϥογϡ͠ͳ͍͔Βɺ 
 ҆શɻ

12. ΞϓϦ͕Ϋϥογϡ͠ͳ͍͔Βɺ 
 ҆શʜͳͷ͔ʁ

13. ͦ΋ͦ΋ɺ҆શͬͯɺͳʹʁ

14. ੲɺ0CK$
    ͔Β
    4XJGU
    ʹҠߦͨ࣌͠ͷ࿩˞ w αʔό͔Βը૾σʔλͱදࣔαΠζΛऔಘ͢Δॲཧ͕͋ͬͨ
    w αΠζσʔλ͸෯ߴͦ͞ΕͧΕ
    0CK$
    ͷίʔυͰ
    intValue
    Ͱऔಘͯͨ͠
    w 4XJGU
    Խ͢Δͱ͖͸Կ΋ߟ͑ͣʹ
    as? Int ?? 0
    Ͱॲཧͯͨ͠
    

    w ϦϦʔεޙɺҰ෦ͷը૾ͷΈΞεϖΫτൺ͕มΘͬͯ͠·ͬͨࣄ͕݅ൃੜ
    w ௐࠪͨ͠Βɺαʔό͔Βؼ͖ͬͯͨσʔλ͕ͳ͔ͥจࣈྻσʔλͩͬͨͨ Ίɺ0CK$
    ͸ࣗಈม׵ͯ͘͠Ε͕ͨ
    4XJGU
    ͸ܕʹݫ͍ͨ͠Ίࣗಈม׵ͯ͘͠ Εͣɺ?? 0
    ʹΑͬͯ
    0
    ͕୅ೖ͞Εͨ
    w ෯
    0
    ߴ͞
    0
    ͷ৔߹͸σϑΥϧταΠζͰදࣔ͢Δॲཧ͕͋ͬͨͨΊɺςε τσʔλͰಈ࡞֬ೝ͢Δͱ͖͸શ͘ؾ͔ͮͳ͔ͬͨ ˞
    ࣮࿩Ͱ͢

15. Ϋϥογϡ͸͠ͳ͔͕ͬͨɺ 
 !
    Λආ͚Δ͋·Γɺ 
 ٯʹόάͷൃݟΛ஗Βͤͨ

16. ʮ҆શʯͳιʔείʔυ͸ɺ
    όάΛຊ൪ϦϦʔεલʹ 
 ؾ͔ͮͤΔ΂͖ɻ

17. ͜ͷίʔυͬͯɺ҆શʁ func doSomething() { let image = UIImage(named: "ImageName") ??

    UIImage() // do something with image }

18. ͜ͷίʔυͷํ͕ɺ҆શ func doSomething() { let image = UIImage(named: "ImageName")! //

    do something with image } όϯυϧʹೖͬͯͳ͍ͱ͍͚ͳ͍͸ͣͷ 
 ը૾Ϧιʔε͔ͩΒɺ
    ສ͕Ұೖͬͯͳ͔ͬͨΒͦΕ͸όάͳͷͰ
    ಈ࡞֬ೝͰΫϥογϡͯ͘͠Εͨํ͕ 
 ؾ෇͖΍͍͢

19. ͜ͷίʔυͬͯɺ҆શʁ func doSomething() { guard let appDelegate = UIApplication .shared.delegate

    as? AppDelegate else { return } // do something with appDelegate }

20. ͜ͷίʔυͷํ͕ɺ҆શ func doSomething() { let appDelegate = UIApplication.shared.delegate as! AppDelegate

    // do something with appDelegate } ϓϩδΣΫτͷ࡞Γ͕ 
 ͜ͷΑ͏ʹͳͬͯΔ͸ͣͳͷͰɺ
    ສ͕Ұ͜ΕͰμ΢ϯΩϟετͰ͖ͳ͔ͬͨΒ
    ઈରϓϩάϥϜ͕Կ͔ؒҧͬͯΔ͸͔ͣͩΒɺ
    ಈ࡞֬ೝͰΫϥογϡͯ͘͠Εͨํ͕
    ؾ෇͖΍͍͢

21. !
    Λ࢖͏΂͖ॴͰ࢖ͬͨํ͕ɺ
    όάͷૣظൃݟʹͭͳ͕Γɺ
    Ή͠Ζ҆қͳѲΓ௵͠ΑΓ҆શɻ

22. ౰વɺཚ༻ͯ͠͸͍͚ͳ͍ɻ

23. ͜ͷίʔυͬͯɺ҆શʁ func doSomething(with data: Data) { do { let decoder

    = JSONDecoder() let response = try decoder.decode(Response.self, from: data) // do something with response } catch { debugPrint(error) return } }

24. ͜ͷίʔυͷํ͕ɺ҆શ func doSomething(with data: Data) { do { let decoder

    = JSONDecoder() let response = try decoder.decode(Response.self, from: data) // do something with response } catch { assertionFailure("\(error)") return } } ԾʹαʔόͷσʔλͱҰக͠ͳ͔ͬͨΒ
    BTTFSUJPO'BJMVSF
    ʹΑͬͯ
    σόοάϏϧυ͚ͩΫϥογϡͯ͠ 
 όάΛૣظൃݟ͠ɺ
    ຊ൪ͷϦϦʔεϏϧυʹ͸Өڹͳ͠ɻ
    ʢ΋ͪΖΜ͜͜ͰߋʹΤϥʔΞϥʔτΛ 
 Ϣʔβʹදࣔͤͨ͞Βͳ͓ྑ͠ʣ

25. ͜ͷίʔυ͸ɺ͕͢͞ʹ҆શͰ͸ͳ͍ func doSomething(with data: Data) { let decoder = JSONDecoder()

    let response = try! decoder.decode(Response.self, from: data) // do something with response } ສ͕Ұαʔόଆ͕όάΛى͜Γ 
 ຊདྷͷ࢓༷ͱ͸ҧ͏ܕͷϨεϙϯε͕ 
 ؼ͖ͬͯͨΒ 
 ΞϓϦ͕ଈΫϥογϡ͢ΔͷͰ 
 ྲྀੴʹྑ͘ͳ͍

26. 5*14ᶃ w ͦΕͰ΋΍͸ΓͲ͏ͯ͠΋ຊ൪ϦϦʔεͰΫϥογϡ ͯ͠ཉ͘͠ͳ͍ɻԿ͔ํ๏͋Δʁ
    w assertionFailure
    Λ࢖͑͹ɺσόοάϏϧυͩ ͚ΫϥογϡͰ͖ΔͷͰɺͥͻ׆༻͠·͠ΐ͏ɻ
    w ྫɿ
    let

    image = UIImage(named: "ImageName") ?? { assertionFailure("ImageName not found") return UIImage() }()

27. 5*14ᶄ w ଞʹ΋Ͳ͔͜ੵۃతʹ
    !
    Λ࢖ͬͨํ͕৔໘͋Δʁ
    w ςετίʔυ΋Ή͠ΖੵۃతʹόάΛؾ෇͖͍ͨ͠ ຊ൪ΞϓϦʹҰ੾Өڹ͠ͳ͍ͷͰɺੵۃతʹ
    !
    Λ࢖ ͑Δ͜ͱ͕ଟ͍Ͱ͢ɻ
    w ͨͩ͠Ϋϥογϡ͢Δͱޙଓͷίʔυ΋ಈ͔ͳ͘ ͳΔͷͰɺ৔ॴʹΑͬͯ͸
    XCTFail
    Λ࢖ͬͨํ

    ͕͍͍͜ͱ΋͋Γ·͢
    w 1MBZHSPVOE
    ͱ͔ͷຊ൪ΞϓϦؔ܎ͳࣗ͘෼Ͱखܰ ͳಈ࡞֬ೝ͍ͨ࣌͠΋΋ͪΖΜੵۃతʹ࢖ͬͯΑ͠

28. !
    Λա౓ʹڪΕͣʹ
    ͏·͘׆༻ͯ͠
    όάΛૣظʹ௵͠·͠ΐ͏