4.外观模式

约 311 字大约 1 分钟

2026-02-27

外观模式（Facade Pattern）的主要目的是：把多步骤流程封装成一个入口，让调用方不需要关心内部细节，直接通过外观对象完成业务操作，从而降低调用复杂度和耦合度

适合使用外观模式的场景

下单流程：把库存校验、价格计算、优惠券、支付、通知进行封装
文件上传：把分片、重试、秒传、进度、合并、回调等功能进行封装

子系统定义

interface SubmitOrderParams {
    orderId: string;
    skuId: string;
    count: number;
    amount: number;
    userId: string;
}

class InventoryService {
    check(skuId: string, count: number): boolean {
        console.log("检查库存", skuId, count);
        return true;
    }
}

class PaymentService {
    pay(orderId: string, amount: number): boolean {
        console.log("支付成功", orderId, amount);
        return true;
    }
}

class NotifyService {
    send(userId: string, message: string): void {
        console.log("发送通知", userId, message);
    }
}

外观类

class OrderFacade {
    constructor(
        private inventory = new InventoryService(),
        private payment = new PaymentService(),
        private notify = new NotifyService(),
    ) {}

    submit(params: SubmitOrderParams): void {
        const inStock = this.inventory.check(params.skuId, params.count);
        if (!inStock) {
            throw new Error("库存不足");
        }

        const paid = this.payment.pay(params.orderId, params.amount);
        if (!paid) {
            throw new Error("支付失败");
        }

        this.notify.send(params.userId, "下单成功");
    }
}

使用示例

new OrderFacade().submit({
    orderId: "O-1001",
    skuId: "SKU-1",
    count: 1,
    amount: 99,
    userId: "U-1",
});

在这个案例中把 inventory.check、payment.pay、notify.send 收敛成一步 orderFacade.submit