从职责链看电商购物优惠模式的应用

2024-01-01 00:53:53

职责链模式是一种设计模式，它允许您将请求沿着链式结构传递，直到找到可以处理请求的组件。这种模式可以使您的代码更具模块化和可扩展性，因为它允许您在不修改现有代码的情况下添加新组件。

在电商购物中，职责链模式可以用于构建一个灵活的优惠系统。例如，我们可以定义一个基类DiscountHandler，它包含处理折扣请求的通用方法。然后，我们可以创建多个子类来处理不同类型的折扣，例如FixedDiscountHandler和PercentageDiscountHandler。

class DiscountHandler {
    public next: DiscountHandler | null = null;

    public handle(request: DiscountRequest): DiscountResponse | null {
        if (this.canHandle(request)) {
            return this.applyDiscount(request);
        } else if (this.next) {
            return this.next.handle(request);
        } else {
            return null;
        }
    }

    protected canHandle(request: DiscountRequest): boolean {
        return false;
    }

    protected applyDiscount(request: DiscountRequest): DiscountResponse {
        return {
            discountAmount: 0,
            discountedPrice: request.originalPrice,
        };
    }
}

class FixedDiscountHandler extends DiscountHandler {
    private fixedDiscountAmount: number;

    constructor(fixedDiscountAmount: number) {
        super();
        this.fixedDiscountAmount = fixedDiscountAmount;
    }

    protected canHandle(request: DiscountRequest): boolean {
        return true;
    }

    protected applyDiscount(request: DiscountRequest): DiscountResponse {
        const discountAmount = Math.min(this.fixedDiscountAmount, request.originalPrice);
        const discountedPrice = request.originalPrice - discountAmount;

        return {
            discountAmount,
            discountedPrice,
        };
    }
}

class PercentageDiscountHandler extends DiscountHandler {
    private percentageDiscount: number;

    constructor(percentageDiscount: number) {
        super();
        this.percentageDiscount = percentageDiscount;
    }

    protected canHandle(request: DiscountRequest): boolean {
        return true;
    }

    protected applyDiscount(request: DiscountRequest): DiscountResponse {
        const discountAmount = request.originalPrice * this.percentageDiscount;
        const discountedPrice = request.originalPrice - discountAmount;

        return {
            discountAmount,
            discountedPrice,
        };
    }
}

// 使用折扣处理链计算折扣
const discountRequest = {
    originalPrice: 100,
};

const fixedDiscountHandler = new FixedDiscountHandler(50);
const percentageDiscountHandler = new PercentageDiscountHandler(0.2);

fixedDiscountHandler.next = percentageDiscountHandler;

const discountResponse = fixedDiscountHandler.handle(discountRequest);

console.log(`折扣金额：${discountResponse.discountAmount}`);
console.log(`折扣后价格：${discountResponse.discountedPrice}`);