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܅͚ͩͷΦϦδφϧ
async / await Λ࡞Ζ͏
susisu
2025-05-24 TSKaigi 2025
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݁: TypeScript ໘ന͍
ؾָʹฉ͍͍ͯͩ͘͞
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• id:susisu / @susisu / @susisu2413
• גࣜձࣾͯͳ
Web ΞϓϦέʔγϣϯΤϯδχΞ
• TypeScript ͷݶքΛ߈ΊΔͷ͕झຯͰ͢
͜Μʹͪ
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ϦαʔνͳͲͷΠϯλϏϡʔ݁ՌͷੳϓϩηεΛࢧԉ͢ΔൃੳιϦϡʔγϣϯ
TypeScript / Next.js / Prisma Ͱ։ൃ͍ͯ͠·͢
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No content
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ࠓ͢͜ͱ
ᶃ async / await Λ
δΣωϨʔλͰ࠶࣮
ᶄ TypeScript ʹΑΔܕ͚
ᶅ Ԡ༻ͦͷ 1: Result ܕ
ᶆ Ԡ༻ͦͷ 2: ΤϑΣΫτ
JS
TS
ᶃ
ᶄ
ᶅ
ᶆ
async / await
δΣωϨʔλ
Result ܕ
ΤϑΣΫτ
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ࠓ͢͜ͱ
ᶃ async / await Λ
δΣωϨʔλͰ࠶࣮
ᶄ TypeScript ʹΑΔܕ͚
ᶅ Ԡ༻ͦͷ 1: Result ܕ
ᶆ Ԡ༻ͦͷ 2: ΤϑΣΫτ
JS
ᶃ
async / await
δΣωϨʔλ
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ࠓ͢͜ͱ
ᶃ async / await Λ
δΣωϨʔλͰ࠶࣮
ᶄ TypeScript ʹΑΔܕ͚
ᶅ Ԡ༻ͦͷ 1: Result ܕ
ᶆ Ԡ༻ͦͷ 2: ΤϑΣΫτ
JS
TS
ᶃ
ᶄ
async / await
δΣωϨʔλ
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ࠓ͢͜ͱ
ᶃ async / await Λ
δΣωϨʔλͰ࠶࣮
ᶄ TypeScript ʹΑΔܕ͚
ᶅ Ԡ༻ͦͷ 1: Result ܕ
ᶆ Ԡ༻ͦͷ 2: ΤϑΣΫτ
JS
TS
ᶃ
ᶄ
ᶅ
async / await
δΣωϨʔλ
Result ܕ
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ࠓ͢͜ͱ
ᶃ async / await Λ
δΣωϨʔλͰ࠶࣮
ᶄ TypeScript ʹΑΔܕ͚
ᶅ Ԡ༻ͦͷ 1: Result ܕ
ᶆ Ԡ༻ͦͷ 2: ΤϑΣΫτ
JS
TS
ᶃ
ᶄ
ᶅ
ᶆ
async / await
δΣωϨʔλ
Result ܕ
ΤϑΣΫτ
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ᶃ async / await Λ
δΣωϨʔλͰ࠶࣮
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async / await
• Promise ΛͬͨίʔυΛݟ௨͠ྑ͘ॻͨ͘Ίʹ async / await ෆՄܽ
// before
doX().then((x) =>
doY(x).then((y) =>
doZ(y).then((z) =>
// ...
)
)
);
// after
const x = await doX();
const y = await doY(x);
const z = await doZ(y);
// ...
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async / await ͷྺ࢙
• Promise ͷඪ४Խ͔Β async / await ͷඪ४Խ·ͰλΠϜϥά͕͋ͬͨ
• Promise: ES2015
• async / await: ES2017
• ਓʑτϥϯεύΠϥΛͬͯ async / await ΛઌऔΓ͍ͯͨ͠
• Babel, TypeScript
• ͋Δ͍δΣωϨʔλΛͬͯ async / await ͬΆ͍ίʔυΛॻ͍͍ͯͨ
• tj/co, Koa
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δΣωϨʔλ
• ES2015 Ͱඪ४Խ͞Εͨݴޠػೳ
• δΣωϨʔλؔ function* ͱ yield ࣜͰΠςϨʔλΛखଓ͖తʹهड़Ͱ͖Δ
• ͜Εதஅɾ࠶։Ͱ͖Δܭࢉ (ίϧʔνϯ) ͱͯ͠ݟΔ͜ͱͰ͖Δ
function* range(from, to, step = 1) {
for (let n = from; n < to; n += step) {
yield n;
}
}
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δΣωϨʔλؔͷதஅɾ࠶։
function* myFunc() {
const x = yield "X";
const y = yield "Y";
return x + y;
}
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δΣωϨʔλؔͷதஅɾ࠶։
function* myFunc() {
const x = yield "X";
const y = yield "Y";
return x + y;
}
const gen = myFunc();
← ·࣮ͩߦ͞Ε͍ͯͳ͍
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δΣωϨʔλؔͷதஅɾ࠶։
function* myFunc() {
const x = yield "X";
const y = yield "Y";
return x + y;
}
const gen = myFunc();
gen.next(); // { done: false, value: "X" }
← yield Ͱதஅ
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δΣωϨʔλؔͷதஅɾ࠶։
function* myFunc() {
const x = yield "X"; // x = 1
const y = yield "Y";
return x + y;
}
const gen = myFunc();
gen.next(); // { done: false, value: "X" }
gen.next(1); // { done: false, value: "Y" }
← ࠶։͞Εͯ;ͨͨͼ yield Ͱதஅ
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δΣωϨʔλؔͷதஅɾ࠶։
function* myFunc() {
const x = yield "X"; // x = 1
const y = yield "Y"; // y = 2
return x + y;
}
const gen = myFunc();
gen.next(); // { done: false, value: "X" }
gen.next(1); // { done: false, value: "Y" }
gen.next(2); // { done: true, value: 3 }
← return Ͱऴྃ
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async / await ͷ࠶࣮
• δΣωϨʔλؔͷதஅɾ࠶։Λར༻͢Εɺasync / await Λ࠶ݱͰ͖ͦ͏
• await Promise ͷྃ·Ͱؔͷ࣮ߦΛதஅ͢Δ͜ͱʹ΄͔ͳΒͳ͍
• جຊతͳΞΠσΞ:
• Promise Λ yield ͯ͠ܭࢉΛதஅ
• Promise ͕ྃͨ͠ΒܭࢉΛ࠶։
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async / await ͷ࠶࣮
async function myFunc() {
const x = await doX();
const y = await doY(x);
return y;
}
const promise = myFunc();
function* myFunc() {
const x = yield doX();
const y = yield doY(x);
return y;
}
const promise = run(myFunc());
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async / await ͷ࠶࣮
async function myFunc() {
const x = await doX();
const y = await doY(x);
return y;
}
const promise = myFunc();
function* myFunc() {
const x = yield doX();
const y = yield doY(x);
return y;
}
const promise = run(myFunc());
→ ͍͍ײ͡ʹδΣωϨʔλΛ࣮ߦͯ͘͠ΕΔؔ run() Λ࣮͢Δ
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async / await ͷ࠶࣮
• εϥΠυதͷίʔυͷશ൛ҎԼͷϦϙδτϦʹ͋Γ·͢
• https://github.com/susisu/tskaigi2025
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run() ͷ࣮ (1/3)
function run(comp) {
function onFulfilled(value) { // Promise 成功時の処理
let res;
try {
res = comp.next(value); // 計算を再開
} catch (e) {
return Promise.reject(e); // throw
}
if (res.done) return Promise.resolve(res.value); // return
return res.value.then(onFulfilled, onRejected); // yield
}
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run() ͷ࣮ (1/3)
function run(comp) {
function onFulfilled(value) { // Promise 成功時の処理
let res;
try {
res = comp.next(value); // 計算を再開
} catch (e) {
return Promise.reject(e); // throw
}
if (res.done) return Promise.resolve(res.value); // return
return res.value.then(onFulfilled, onRejected); // yield
}
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run() ͷ࣮ (1/3)
function run(comp) {
function onFulfilled(value) { // Promise 成功時の処理
let res;
try {
res = comp.next(value); // 計算を再開
} catch (e) {
return Promise.reject(e); // throw
}
if (res.done) return Promise.resolve(res.value); // return
return res.value.then(onFulfilled, onRejected); // yield
}
δΣωϨʔλ͔ؔΒͷԠ
throw, return, yield ͷ 3 ௨Γ͕͋ΓಘΔ
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run() ͷ࣮ (2/3)
function onRejected(error) { // Promise 失敗時の処理
let res;
try {
res = comp.throw(error); // 計算を再開
} catch (e) {
return Promise.reject(e); // throw
}
if (res.done) return Promise.resolve(res.value); // return
return res.value.then(onFulfilled, onRejected); // yield
}
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run() ͷ࣮ (2/3)
function onRejected(error) { // Promise 失敗時の処理
let res;
try {
res = comp.throw(error); // 計算を再開
} catch (e) {
return Promise.reject(e); // throw
}
if (res.done) return Promise.resolve(res.value); // return
return res.value.then(onFulfilled, onRejected); // yield
}
onFul
fi
lled ͱͷ͚ࠩͩ͜͜
yield ͷՕॴͰ throw ͢Δ
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run() ͷ࣮ (3/3)
// 計算を先頭から開始
return onFulfilled();
}
function* myFunc() {
const x = yield doX();
const y = yield doY(x);
return y;
}
const promise = run(myFunc());
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͜͜·Ͱͷ·ͱΊ
• δΣωϨʔλதஅɾ࠶։Ͱ͖Δܭࢉͱͯ͠ݟΔ͜ͱ͕Ͱ͖Δ
• ͜ΕΛ͑ async / await ૬ͷͷΛ࠶࣮Ͱ͖Δ
• ͜͜·Ͱશͯ JavaScript ͷ
• ࣮͜ͷ··ͩͱ yield ࣜʹ͏·͘ܕ͕͚ΒΕͳ͍ʂ
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ᶄ TypeScript ʹΑΔܕ͚
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TypeScript ʹΑΔܕ͚
function* myFunc() {
const x = yield doX();
const y = yield doY(x);
return y;
}
const promise = run(myFunc());
• yield ࣜʹܕ͕͚ΒΕΔঢ়ଶΛࢦ͢
• (run() ͷ࣮෦ʹର͢Δܕ͚ࢦ͞ͳ͍)
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yield ࣜʹର͢Δܕ͚ͷน
• yield ࣜʹܕΛ͚Δʹ͋ͨͬͯ 2 ͭͷน͕͋Δ
1. δΣωϨʔλ͕ඞܾͣ·ͬͨํ๏Ͱ࣮ߦ͞ΕΔอূ͕ͳ͍
2. yield ࣜ͝ͱʹҟͳΔܕ͕͚ΒΕͳ͍
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1. ܾ·ͬͨํ๏Ͱ࣮ߦ͞ΕΔอূ͕ͳ͍
function* myFunc() {
const x = yield doX();
const y = yield doY(x);
return y;
}
const promise = run(myFunc()); // run() を使っているなら OK
const what = [...myFunc()]; // そうでないならダメ
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1. ܾ·ͬͨํ๏Ͱ࣮ߦ͞ΕΔอূ͕ͳ͍
function* myFunc() {
const x = yield doX();
const y = yield doY(x);
return y;
}
const promise = run(myFunc()); // run() を使っているなら OK
const what = [...myFunc()]; // そうでないならダメ
→ نͱ͍͏͜ͱʹͯ͠͠·͏...
• ໓ଟʹΒͳ͍Ͱ͠ΐ͏ / ඞཁʹͳͬͨΒ Linter Λ࡞Ζ͏
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2. yield ࣜ͝ͱʹҟͳΔܕ͕͚ΒΕͳ͍
• δΣωϨʔλͷܕ Generator
• T ... yield a ͷ a ͷܕ
• TReturn ... return a ͷ a ͷܕ
• TNext ... gen.next(b) ͷ b ͷܕ = yield a ͷܕ
function* myFunc(): Generator {
// ...
}
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2. yield ࣜ͝ͱʹҟͳΔܕ͕͚ΒΕͳ͍
• yield ࣜͷܕ = TNext ͕ 1 छྨ͔͠ͳ͍
• ҎԼͷίʔυͰݴ͏ͱ x ͱ y ͷܕ͕ಉ͡ʹͳͬͯ͠·͏
function* myFunc(): Generator {
const x = yield doX(); // x: TNext
const y = yield doY(x); // y: TNext
return y;
}
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• yield ࣜͷܕ = TNext ͕ 1 छྨ͔͠ͳ͍
• ҎԼͷίʔυͰݴ͏ͱ x ͱ y ͷܕ͕ಉ͡ʹͳͬͯ͠·͏
→ yield* ࣜΛ͏
function* myFunc(): Generator {
const x = yield doX(); // x: TNext
const y = yield doY(x); // y: TNext
return y;
}
2. yield ࣜ͝ͱʹҟͳΔܕ͕͚ΒΕͳ͍
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yield* ࣜΛ͏
• yield* iter Iterable ΛδΣωϨʔλؔͰల։͢Δߏจ
• yield* iter ͷܕ iter ʹԠܾͯ͡·Δ
• iter ͷܕ͕ Iterable ͷͱ͖ɺyield* iter ͷܕ SReturn
• → ࣜ͝ͱʹҟͳΔܕΛ࣋ͯΔ
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yield* ࣜΛ͏
• yield* ࣜʹ༩͑Δ Iterable Ͱ͋Δඞཁ͕͋Δ
• ୯७ʹ yield a Λ yield* a ͷΑ͏ʹஔ͖͑Δ͜ͱͰ͖ͳ͍
• yield* toIterable(a) ͷΑ͏ʹ Iterable ʹม͠ͳ͍ͱ͍͚ͳ͍
• มͳΜͰྑ͍Θ͚Ͱͳ͍
• ݩʑͷ yield a ͱஔ͖͑ޙͷ yield* toIterable(a) ಉ͡ಈ͖Λͯ͠΄͍͠
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Iterable ͷม
type Comp = Generator, T, any>;
function* waitFor(promise: Promise): Comp> {
return yield promise;
}
• ୯ҰͷΛ yield ͠ɺͦͷΛ return ͢Δ͚ͩͷδΣωϨʔλΛ࡞Δ
• yield* waitFor(a) yield a ͱಉ͡ಈ࡞Λ͢Δ͕ɺܕใ͕૿͍͑ͯΔ
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Iterable ʹม͢Δ
declare function run(comp: Comp): Promise>;
function* myFunc(): Comp {
const x = yield* waitFor(doX()); // x: X
const y = yield* waitFor(doY(x)); // y: Y
return y;
}
const promise = run(myFunc()); // promise: Promise
• run() ʹରͯ͠֎͔ΒܕΛ͚ͭΔ͚ͩͰ
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͜͜·Ͱͷ·ͱΊ
• ࣗ࡞ async / await ʹܕΛ͚Δʹ 2 ͭͷน͕͋Δ
• δΣωϨʔλ͕Ͳ͏ݺΕΔ͔อূ͕ͳ͍
• yield ࣜ͝ͱʹҟͳΔܕ͕͚ΒΕͳ͍
• લऀنԽͰΧόʔՄೳɺޙऀ yield ࣜͷΘΓʹ yield* ࣜΛ͏͜ͱͰ
Γӽ͑ΒΕΔ
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ᶅ Ԡ༻ͦͷ 1: Result ܕ
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Promise Ҏ֎ͷԠ༻
• ͜͜·ͰͷςΫχοΫ Promise ΛͬͨॲཧҎ֎ʹԠ༻͕Մೳ
• δΣωϨʔλ͔Β yield ͞ΕͨͱɺδΣωϨʔλͷΓͷܭࢉΛɺ
্खʹ͚ͬͭ͘Δ͜ͱ͕Ͱ͖ͨΒΑ͍ (= Ϟφυ)
• Promise ͷ߹ then() ͕͜ͷׂΛ͍࣋ͬͯΔ
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Promise Ҏ֎ͷԠ༻
• ྫ͑ Result ܕ͜Εʹͯ·Δ
• then() ʹରԠ͢ΔͷԼͷΑ͏ͳ݅ذ
type Result = Ok | Err;
if (!res.isOk) return res;
return cont(res.value);
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Result ܕͷԠ༻
• Promise Ͱ then() ͕ await (yield*) ʹஔ͖͑ΒΕͨ
// before
doX().then((x) =>
doY(x).then((y) =>
doZ(y).then((z) =>
// ...
)
)
);
// after
const x = await doX();
const y = await doY(x);
const z = await doZ(y);
// ...
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Result ܕͷԠ༻
• Result Ͱಉ͡Α͏ʹஔ͖͑ΒΕΔ → ΤϥʔϋϯυϦϯάΛ؆ུԽ
// before
const x = doX();
if (!x.isOk) return x;
const y = doY(x.value);
if (!y.isOk) return y;
const z = doZ(y.value);
if (!z.isOk) return z;
// ...
// after
const x = yield* doX();
const y = yield* doY(x);
const z = yield* doZ(y);
// ...
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Result ܕͷԠ༻
• ׂ࣮Ѫ (ઌ΄Ͳͱಉ͡ susisu/tskaigi2025 ʹશ൛͕͋Γ·͢)
• run() ͷఆٛ Promise ͷ࣌ͱ΄΅ಉ͡ (then() ͕ҟͳΔ͚ͩ)
type Comp = Generator, T, any>;
declare function run(comp: Comp): Result;
function* myFunc(): Comp { /* ... */ }
const result = run(myFunc()); // result: Result
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Result ܕࣗମΛ Iterable ʹ͢Δ
• Promise ͱҟͳΓɺResult ܕࣗମΛ Iterable ʹͰ͖Δ
• yield* ࣜΛ͏ͱ͖ͷมΛखͰॻ͘ඞཁ͕ͳ͘ͳͬͯศར
class Ok {
// ...
*[Symbol.iterator](): Comp {
return yield this;
}
}
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͜͜·Ͱͷ·ͱΊ
• δΣωϨʔλΛͬͨςΫχοΫ Promise Ҏ֎ʹԠ༻͕Մೳ
• yield ͞ΕͨͱΓͷܭࢉΛ্ख͚ͬͭ͘͘ΒΕͨΒྑ͍ (Ϟφυ)
• ྫͱͯ͠ Result ܕͷ߹Λհ
• ଞʹ͍Ζ͍Ζ
• neverthrow, E
ff
ect ͳͲͷϥΠϒϥϦ
• ύʔαίϯϏωʔλ
• etc.
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ᶆ Ԡ༻ͦͷ 2: ΤϑΣΫτ
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ΤϑΣΫτ
• ;ͭ͏ϓϩάϥϜ࣮ߦ͢Δͱ༷ʑͳΤϑΣΫτΛൃੜͤ͞Δ
• ը໘ʹจࣈը૾Λදࣔ͢ΔɺϑΝΠϧΛಡΈॻ͖͢Δɺ
ωοτϫʔΫϦΫΤετΛߦ͏ɺݱࡏ࣌ࠁΛऔಘ͢ΔɺͳͲͳͲ
• ͜ΕΒͷΤϑΣΫτΛ্खʹऔΓѻ͍͍ͨ → ΤϑΣΫτγεςϜ
• ϓϩάϥϜͷͲͷ෦͕ωοτϫʔΫϦΫΤετΛߦ͏ͷ͔Γ͍ͨ
• ςετͰωοτϫʔΫϦΫΤετΛϞοΫͰ༻͍ͨ͠
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• ͜Μͳ;͏ʹϓϩάϥϜ͕ॻ͚Δͱͨ͠Βʁ
ΤϑΣΫτγεςϜ
// 発生し得るエフェクトの種類を型でトラッキング
function* main(): Eff {
const icon = yield* httpGet("https://susisu.ch/icon.svg");
yield* writeFile("./icon.svg", icon);
}
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• ͜Μͳ;͏ʹϓϩάϥϜ͕ॻ͚Δͱͨ͠Βʁ
ΤϑΣΫτγεςϜ
// 型に現れないエフェクトを発生させたらコンパイルエラー
function* main(): Eff {
const icon = yield* httpGet("https://susisu.ch/icon.svg");
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
yield* writeFile("./icon.svg", icon);
}
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ΤϑΣΫτγεςϜ
• ͜Μͳ;͏ʹϓϩάϥϜ͕ॻ͚Δͱͨ͠Βʁ
// 通常は実際に読み書き
runAsync(
interpret(main(), {
net: interpretNet,
fs: interpretFs,
}),
);
// テストではモック実装
runPure(
interpret(main(), {
net: mockNet,
fs: mockFs,
}),
);
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ΤϑΣΫτγεςϜ
• ͜Μͳ;͏ʹϓϩάϥϜ͕ॻ͚Δͱͨ͠Βʁ
• → ॻ͚·ͨ͠ (࣮ݧతͳϥΠϒϥϦΛ࡞Γ·ͨ͠)
• https://github.com/susisu/e
ff
ectful
• ͜͜·Ͱʹհͨ͠ͷશ࣮ͯࡍʹಈ࡞͢Δίʔυ
• ཧతʹ Algebraic E
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ects & Handlers ͱݺΕΔύϥμΠϜ
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ΤϑΣΫτγεςϜͷ࣮
• δΣωϨʔλͷܕఆٛ Promise Result ͷ߹ͱجຊಉ͡
• ͨͩ͠۩ମతͳσʔλ (Ϟφυ) ͷ෦ΤϑΣΫτͱͯ͠நԽ͓͍ͯͯ͠ɺ
ޙ͔Β࣮ߦ͢ΔՕॴ (ϋϯυϥ) Ͱܾఆ͢Δ
// before
type Comp = Generator, T, any>;
type Comp = Generator, T, any>;
// after
type Eff = Generator, T, any>;
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࣌ؒͶ͐ʔ
• ໘ന͍͜ͱ͕ͨ͘͞Μ͋Δ͚Ͳ͕࣌ؒ͢Γͳ͍ʂ
• ࣮ʹͬͨςΫχοΫ
• ϢχΦϯܕͰΤϑΣΫτͷ row Λૉʹදݱ (ׂͱ TypeScript ಛ༗)
• interface ͷએݴϚʔδΛͬͨߴ֊ܕ (ΤϑΣΫτͷநԽʹඞཁ)
• GADT (நԽͨ͠ΤϑΣΫτͷΓͷܕΛݻఆ)
• ΤϑΣΫτγεςϜΛͬͯ۩ମతʹԿΛ͢Δͷ͔ʁ (͑Δͷ͔ʁ)
• Ask the Speaker ࠙ձͰ͠·͠ΐ͏ :pray:
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·ͱΊ
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·ͱΊ (1/2)
• δΣωϨʔλؔதஅɾ࠶։Ͱ͖Δܭࢉͱͯ͠ݟΔ͜ͱ͕Ͱ͖Δ
• ͜ΕΛ͑ async / await ૬ͷه๏Λࣗ࡞Ͱ͖Δ
• TypeScript Ͱͪΐͬͱ͓ͨ͠·͡ͳ͍Ͱ֓Ͷ্ख͘ܕΛ͚ΒΕΔ
• yield Λ yield* ʹஔ͖͑Δ / ͦͷͨΊʹ Iterable ʹม͢Δ
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·ͱΊ (2/2)
• δΣωϨʔλΛͬͨςΫχοΫ Promise Ҏ֎ʹԠ༻͕Մೳ
• yield ͞ΕͨͱΓͷܭࢉΛ্ख͚ͬͭ͘͘ΒΕͨΒྑ͍ (Ϟφυ)
• ۩ମతʹ Result ܕͳͲ
• ͞Βʹ Algebraic E
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ects ͷΑ͏ͳͷ࣮ݱͰ͖Δ
• TypeScript ໘ന͍