20250610 関数型DDD 11

Transcript

1. DDD
2. લճ
3. ΤϥʔΛ෼ྨ
4. υϝΠϯΤϥʔ υϝΠϯϞσϦϯάʹ૊Έࠐ ΈɺܕγεςϜ಺ʹจॻԽ
5. ύχοΫ ྫ֎Λൃੜͤ͞ɺ࠷্ҐͰิ ଍
6. ΠϯϑϥετϥΫ νϟΤϥʔ ΞʔΩςΫνϟʹΑΔ େମ͸υϝΠϯΤϥʔʹؚΊΔ ํ͕໾ཱͭ ↓ ͲΜͳΤϥʔ͕ى͜Δ͔ߟ͑Δ
7. Resultܕ
9. Ξμϓλʔ
10. Լ΋ܨ͛Δ
11. ίʔυͷલʹ
12. ཁ • ೖྗ • 1τϥοΫͷؔ਺ • 2τϥοΫͷ஋ • ग़ྗ • 2τϥοΫ • ͜ΕΛϥοϓͯ͋͛͠Δ • ೖྗΛ2τϥοΫɺग़ྗ΋2τϥοΫͷ ؔ਺ʹม͑ͯ͋͛Δ
13. ࢖͍͍ͨؔ਺ Result<a, e> લͷؔ਺ͷ݁Ռͱ͔ Successͷ৔߹͸ద༻ͯ͠ฦ͢ Errorͷ৔߹͸ͦͷ··errorΛฦ͢ let bind switchFn twoTrackInput = match twoTrackInput with | Ok success -> switchFn success | Error failure -> Error failure
14. αϯϓϧ
15. TS
16. map
17. ҧ͍ OkͰแΜͰฦ͍ͯ͠Δ ͖ͬ͞ͷ͸a->Result ͬͪ͜͸ a->b let map f aResult = match aResult with | Ok success -> Ok (f success) | Error failure -> Error failure
18. ڞ௨ͷΤϥʔܕ
19. Τϥʔ͸ͣͬͱ ԼͷϨʔϧΛ૸Δ
20. ڞ௨ͷΤϥʔܕʹ͢Δඞ ཁ͕͋Δ
21. ͜Εͩͱerror͕ҧ͏ͷͰ߹੒Ͱ͖ͳ͍ type FunctionA = Apple -> Result<Bananas, AppleError> type FunctionB = Bananas -> Result<Cherries, BananaError>
22. ڞ௨ͷΤϥʔܕΛ࡞੒ type FruitError = | AppleErrorCase of AppleError | BananaErrorCase of BananaError
23. let mapError f aResult = match aResult with | Ok success -> Ok success | Error failure -> Error (f failure)
24. let functionA : FunctionA = ... let functionAWithFruitError input = input |> functionA |> Result.mapError (fun appleError -> AppleErrorCase appleError) ͜Ε͸࣍ͷΑ͏ʹ؆ུԽͰ͖·͢ɻ let functionAWithFruitError input = input |> functionA |> Result.mapError AppleErrorCase
25. ߹੒Ͱ͖ΔΑ͏ʹͳͬͨ let functionAWithFruitError input = input |> functionA |> Result.mapError AppleErrorCase // "FruitError"Λ࢖༻͢ΔΑ͏ʹfunctionBΛม׵͢Δ let functionBWithFruitError input = input |> functionB |> Result.mapError BananaErrorCase // ৽͍ؔ͠਺͸ "bind" Ͱ߹੒Ͱ͖Δ let functionAB input = input |> functionAWithFruitError |> Result.bind functionBWithFruitError
26. ͜ΕΛPlaceOrderͱ͔ʹ࢖ ͍ͬͯ͘
27. αϯϓϧఔ౓ʹ // PlaceOrderErrorΛฦ͢Α͏ʹม׵ͨ͠ let validateOrderAdapted input = input |> validateOrder // ݩͷؔ਺ |> Result.mapError PlaceOrderError.Validation // PlaceOrderErrorΛฦ͢Α͏ʹม׵ͨ͠ let priceOrderAdapted input = input |> priceOrder // ݩͷؔ਺ |> Result.mapError PlaceOrderError.Pricing ͜Ε͕ऴΘΔͱɺ࠷ऴతʹ bind Λ࢖ͬͯɺͦΕΒΛ࿈࠯ͤ͞ΒΕΔ let placeOrder unvalidatedOrder = unvalidatedOrder |> validateOrderAdapted // ม׵ޙͷؔ਺ |> Result.bind priceOrderAdapted // ม׵ޙͷؔ਺
28. ྫ֎ॲཧ
29. Try-catch AdapterͰResultܕ let serviceExceptionAdapter2 serviceInfo serviceFn x y = try Ok (serviceFn x y) with | :? TimeoutException as ex -> ... | :? AuthorizationException as ex -> ...
30. ߦ͖ࢭ·Γؔ਺
31. ϩάͱ͔ // string -> unit let logError msg = printfn "ERROR %s" msg
32. લͷ஋Λͦͷ·· ߦ͖ࢭ·Γͷؔ਺ // ('a -> unit) -> ('a -> 'a) let tee f x = f x x
33. mapͰResult
34. // ('a -> unit) -> (Result<'a, 'error> -> Result<'a, 'error>) let adaptDeadEnd f = Result.map (tee f)