20250826 パターンマッチ

Transcript

1. ύλʔϯϚον
2. ύλʔϯϚονͱ͸
3. import { match } from "ts-pattern"; type Stationery = "Pen" | "Pencil"; const useSound = (item: Stationery) => { return match(item) .with("Pen", () => "Χνο") // ϊοΫࣜϖϯͷΠϝʔδ .with("Pencil", () => "αϥαϥ") // ॻ͖৺஍ͷΠϝʔδ .exhaustive(); // શͯͷύλʔϯ͕໢ཏ͞Ε͍ͯΔ͔νΣοΫ͢Δ }; useSound("Pen"); // "Χνο" useSound("Eraser"); // Type Error: '"Eraser"' is not assignable to type 'Stationery'
4. ͍͍ײ͡ͷػೳ
5. TSʹ͸ͳ͍
6. 1. ϥΠϒϥϦ
7. ts-pattern
8. import { match } from "ts-pattern"; type Stationery = "Pen" | "Pencil"; const useSound = (item: Stationery) => { return match(item) .with("Pen", () => "Χνο") // ϊοΫࣜϖϯͷΠϝʔδ .with("Pencil", () => "αϥαϥ") // ॻ͖৺஍ͷΠϝʔδ .exhaustive(); // શͯͷύλʔϯ͕໢ཏ͞Ε͍ͯΔ͔νΣοΫ͢Δ }; useSound("Pen"); // "Χνο" useSound("Eraser"); // Type Error: '"Eraser"' is not assignable to type 'Stationery'
9. 2. ࣗલ
10. ϢχΦϯܕΛ࢖ͬͯ
11. ϔϧύʔؔ਺
12. type Stationery = "Pen" | "Pencil"; const assertNever = (_: never): never => { throw new Error(); }; const check = (item: Stationery) => { switch (item) { case "Pen": return "Χνο"; case "Pencil": return "αϥαϥ"; default: return assertNever(item); } };
13. Ͳ͏ͳΔ͔ʁ
15. Ҿ਺͕never͔͠ड͚औΕͳ͍ ʹ Կ͔ड͚औͬͨΒΤϥʔΛు͘
16. ΍Δͭ΋Γͷ࢖͍ํ
17. ΤϥʔΛϢχΦϯܕͰఆ ٛ
18. type DogError = { kind: "DogError"; message: string; }; type CatError = { kind: "CatError"; message: string; }; type AnimalError = DogError | CatError;
19. ResultΛ࢖͏
20. const checkAnimal = (animal: string): Result<string, AnimalError> => { if (animal === "Dogn") { return err({ kind: "DogError", message: "Invalid animal" }); } if (animal === "Catn") { return err({ kind: "CatError", message: "Invalid animal" }); } return ok("Animal"); };
21. ݁ՌΛύλʔϯϚον
22. const result = checkAnimal("Dog"); result.match( (animal) => { console.log(animal); }, (error) => { switch (error.kind) { case "DogError": return `DogError: ${error.message}`; case "CatError": return `CatError: ${error.message}`; default: return assertNever(error); } } );
23. ΤϥʔΛ໢ཏͯ͠returnՄೳ
24. ଟ͗͢Δ৔߹
26. ଍Γͳ͍৔߹
28. Honoʹ΋࠷దʂ
29. ͳ͸ͣͰͨ͠
30. ܕϑϩϯτʹ౉͢ͷΉͣ