koa3-demo/_backup_old_files/utils/BaseSingleton.js

// 抽象基类，使用泛型来正确推导子类类型
class BaseSingleton {
    static _instance

    constructor() {
        if (this.constructor === BaseSingleton) {
            throw new Error("禁止直接实例化 BaseOne 抽象类")
        }

        if (this.constructor._instance) {
            throw new Error("构造函数私有化失败，禁止重复 new")
        }

        // this.constructor 是子类，所以这里设为 instance
        this.constructor._instance = this
    }

    static getInstance() {
        const clazz = this
        if (!clazz._instance) {
            const self = new this()
            const handler = {
                get: function (target, prop) {
                    const value = Reflect.get(target, prop)
                    if (typeof value === "function") {
                        return value.bind(target)
                    }
                    return Reflect.get(target, prop)
                },
            }
            clazz._instance = new Proxy(self, handler)
        }
        return clazz._instance
    }
}

export { BaseSingleton }