Result を作成する

Result 型を理解したところで、ライブラリのヘルパー関数を使って Result を作成する方法を学びましょう。

`succeed` で成功を表す `Result` を作成する

succeed 関数は成功を表す Result を作成します。

import { import ResultResult } from '@praha/byethrow';

// 値を持つ場合
const const success: Result.Result<42, never>success = import ResultResult.const succeed: <42>(value: 42) => Result.Result<42, never> (+1 overload)succeed(42);
// 型: Result.Result<number, never>

// 値を持たない場合（void）
const const voidSuccess: Result.Result<void, never>voidSuccess = import ResultResult.const succeed: () => Result.ResultFor<never, void, never> (+1 overload)succeed();
// 型: Result.Result<void, never>

非同期値の場合

Promise を渡すと、succeed は自動的に ResultAsync を返します。

import { import ResultResult } from '@praha/byethrow';

const const asyncSuccess: Result.ResultAsync<string, never>asyncSuccess = import ResultResult.const succeed: <Promise<string>>(value: Promise<string>) => Result.ResultAsync<string, never> (+1 overload)succeed(var Promise: PromiseConstructorRepresents the completion of an asynchronous operationPromise.PromiseConstructor.resolve<string>(value: string): Promise<string> (+2 overloads)Creates a new resolved promise for the provided value.
@paramvalue  A promise.@returnsA  promise whose internal state matches the provided promise.resolve('hello'));
// 型: Result.ResultAsync<string, never>

const const resolved: Result.Result<string, never>resolved = await const asyncSuccess: Result.ResultAsync<string, never>asyncSuccess;
// 型: Result.Result<string, never>

`fail` で失敗を表す `Result` を作成する

fail 関数は失敗を表す Result を作成します。

import { import ResultResult } from '@praha/byethrow';

// エラー値を持つ場合
const const failure: Result.Result<never, "Something went wrong">failure = import ResultResult.const fail: <"Something went wrong">(error: "Something went wrong") => Result.Result<never, "Something went wrong"> (+1 overload)fail('Something went wrong');
// 型: Result.Result<never, string>

// 値を持たない場合（void）
const const voidFailure: Result.Result<never, void>voidFailure = import ResultResult.const fail: () => Result.ResultFor<never, never, void> (+1 overload)fail();
// 型: Result.Result<never, void>

非同期エラーの場合

succeed と同様に、Promise を渡すと fail は ResultAsync を返します。

import { import ResultResult } from '@praha/byethrow';

const const asyncFailure: Result.ResultAsync<never, string>asyncFailure = import ResultResult.const fail: <Promise<string>>(error: Promise<string>) => Result.ResultAsync<never, string> (+1 overload)fail(var Promise: PromiseConstructorRepresents the completion of an asynchronous operationPromise.PromiseConstructor.resolve<string>(value: string): Promise<string> (+2 overloads)Creates a new resolved promise for the provided value.
@paramvalue  A promise.@returnsA  promise whose internal state matches the provided promise.resolve('async error'));
// 型: Result.ResultAsync<never, string>

const const resolved: Result.Result<never, string>resolved = await const asyncFailure: Result.ResultAsync<never, string>asyncFailure;
// 型: Result.Result<never, string>

`do` でパイプラインを開始する

do 関数は空のオブジェクトでパイプラインを開始する便利な方法です。

import { import ResultResult } from '@praha/byethrow';

const const start: Result.Result<{}, never>start = import ResultResult.function do(): import("/home/runner/work/byethrow/byethrow/packages/byethrow/dist/esm/result").Result<{}, never>
export do
Alias for succeed({}). Commonly used as a neutral base value in functional chains or monadic pipelines.
@function@exampleimport { Result } from '@praha/byethrow';

const result = Result.do();
// Result.Result<{}, never>
@categoryCreatorsdo();
// 型: Result.Result<{}, never>

これは、オブジェクトを段階的に構築する際に特に便利です（このパターンは後のセクションで詳しく解説します）。

import { import ResultResult } from '@praha/byethrow';

const const result: Result.Result<{
    name: "Alice";
    age: 30;
}, never>
result = import ResultResult.const pipe: <Result.Result<{}, never>, Result.Result<{
    name: "Alice";
}, never>, Result.Result<{
    name: "Alice";
    age: 30;
}, never>>(a: Result.Result<{}, never>, ab: (a: Result.Result<{}, never>) => Result.Result<{
    name: "Alice";
}, never>, bc: (b: Result.Result<{
    name: "Alice";
}, never>) => Result.Result<{
    name: "Alice";
    age: 30;
}, never>) => Result.Result<{
    name: "Alice";
    age: 30;
}, never> (+25 overloads)
pipe(
  import ResultResult.function do(): import("/home/runner/work/byethrow/byethrow/packages/byethrow/dist/esm/result").Result<{}, never>
export do
Alias for succeed({}). Commonly used as a neutral base value in functional chains or monadic pipelines.
@function@exampleimport { Result } from '@praha/byethrow';

const result = Result.do();
// Result.Result<{}, never>
@categoryCreatorsdo(),
  import ResultResult.const bind: <"name", Result.Result<{}, never>, Result.Result<"Alice", never>>(name: "name", fn: (a: {}) => Result.Result<"Alice", never>) => (result: Result.Result<{}, never>) => Result.Result<{
    name: "Alice";
}, never> (+1 overload)
bind('name', () => import ResultResult.const succeed: <"Alice">(value: "Alice") => Result.Result<"Alice", never> (+1 overload)succeed('Alice')),
  import ResultResult.const bind: <"age", Result.Result<{
    name: "Alice";
}, never>, Result.Result<30, never>>(name: "age", fn: (a: {
    name: "Alice";
}) => Result.Result<30, never>) => (result: Result.Result<{
    name: "Alice";
}, never>) => Result.Result<{
    name: "Alice";
    age: 30;
}, never> (+1 overload)
bind('age', () => import ResultResult.const succeed: <30>(value: 30) => Result.Result<30, never> (+1 overload)succeed(30)),
);
// 型: Result.Result<{ name: string; age: number }, never>

リファレンス

関数	目的
succeed(value)	Success の結果を作成
fail(error)	Failure の結果を作成
do()	空のオブジェクトで開始

#Result を作成する

#succeed で成功を表す Result を作成する

#非同期値の場合

#fail で失敗を表す Result を作成する

#非同期エラーの場合

#do でパイプラインを開始する