Singleton実現方法変える

src/features/commands/internal/VoiceChannel/internal/VoiceChannel.class.ts

@@ -1,5 +1,6 @@
 import { Voice } from '@/features/core/index.js';
 import { LogicException } from '@/features/others/Error/LogicException.js';
+import { singleton } from '@/features/others/singleton/index.js';
 
 import { VoiceChannelCommandOptions } from './VoiceChannel.constants.js';
 import type { InteractArgs } from '../../CommandBase/index.js';
@@ -12,7 +13,9 @@ export class VoiceChannel extends CommandBase {
 
   public override async interact({ interaction }: InteractArgs): Promise<void> {
     const subcommand = interaction.options.getSubcommand();
-    const voice = Voice.getInstance();
+    const createVoiceInstance = () => new Voice();
+    const getVoiceInstance = singleton(createVoiceInstance);
+    const voice = getVoiceInstance();
 
     switch (subcommand) {
       case VoiceChannelCommandOptions.join.name:

src/features/core/internal/Voice/internal/Voice.class.ts

@@ -11,25 +11,11 @@ import {
 } from '@/features/library/index.js';
 import { getInteractionMemberId } from '@/features/others/discord/index.js';
 
-/**
- * Singleton class for voice.
- * NOTE: シングルトンの影響で複数サーバにしたときのテストしないと困るかも
- */
 export class Voice {
-  static #instance: Voice | null = null;
   #connection: Array<{
     guildId: string;
     connection: VoiceConnection;
   }> = [];
-  private constructor() {}
-
-  public static getInstance(): Voice {
-    if (Voice.#instance === null) {
-      Voice.#instance = new Voice();
-    }
-
-    return Voice.#instance;
-  }
 
   public async join({
     interaction,

src/features/others/singleton/index.ts

@@ -0,0 +1 @@
+export { singleton } from './internal/singleton.func.js';

src/features/others/singleton/internal/singleton.func.ts

@@ -0,0 +1,9 @@
+type Getter<T> = () => T;
+type Factory<T> = () => T;
+
+export const singleton = <T>(factory: Factory<T>): Getter<T> =>
+  ((): Getter<T> => {
+    let memo: T | null = null;
+
+    return () => (memo ? memo : (memo = factory()));
+  })();

src/features/others/singleton/internal/singleton.spec.ts

@@ -0,0 +1,19 @@
+import { singleton } from './singleton.func.js';
+
+it('not identical', () => {
+  const factory = () => ({});
+
+  const x = factory();
+  const y = factory();
+
+  expect(x).not.toBe(y);
+});
+it('with singleton, identical', () => {
+  const factory = () => ({});
+  const getter = singleton(factory);
+
+  const x = getter();
+  const y = getter();
+
+  expect(x).toBe(y);
+});