3.行为型模式(behavioral 11)

3.1 责任链模式(chain-of-resp)

• 使多个对象都有机会处理请求，从而避免请求的发送者和接受者之间的耦合关系，将这个对象连成一条链，并沿着这条链传递该请求，直到有一个对象处理他为止。

//购物车 商品 添加商品
function ShoppingCart() {
	this.products = []

	this.addProduct = function (p) {
		this.products.push(p)
	}
}
//折扣计算 看是否满足特定的折扣 形成链n->p->none 执行起始的exec 知道有返回
function Discount() {
	this.calc = function (products) {
		var ndiscount = new NumberDiscount()
		var pdiscount = new PriceDiscount()
		var none = new NoneDiscount()

		ndiscount.setNext(pdiscount)
		pdiscount.setNext(none)

		return ndiscount.exec(products)
	}
}

function NumberDiscount() {
	this.next = null
	this.setNext = function (fn) {
		this.next = fn
	}
	this.exec = function (products) {
		var result = 0
		if (products.length > 3) result = 0.05

		return (result += this.next.exec(products))
	}
}

function PriceDiscount() {
	this.next = null
	this.setNext = function (fn) {
		this.next = fn
	}
	this.exec = function (products) {
		var result = 0
		var total = products.reduce(function (a, b) {
			return a + b
		})
		if (total >= 500) {
			result = 0.1
		}
		return result + this.next.exec(products)
	}
}

function NoneDiscount() {
	this.exec = function () {
		return 0
	}
}

module.exports = [ShoppingCart, Discount]

const expect = require('chai').expect
const [ShoppingCart, Discount] = require('../src/behavioral/chain-of-resp/chain-of-resp')

describe('责任链模式 测试', () => {
	it('购物车金额 > $500', () => {
		const discount = new Discount()
		const sc = new ShoppingCart()
		sc.addProduct(1000)
		let resp = discount.calc(sc.products)

		expect(resp).to.equal(0.1)
	})
	it('大于三个商品', () => {
		const discount = new Discount()
		const sc = new ShoppingCart()
		sc.addProduct(100)
		sc.addProduct(100)
		sc.addProduct(100)
		sc.addProduct(100)
		let resp = discount.calc(sc.products)
		expect(resp).to.equal(0.05)
	})
	it('大于三个商品并且 >$500', () => {
		const discount = new Discount()
		const sc = new ShoppingCart()
		sc.addProduct(1000)
		sc.addProduct(100)
		sc.addProduct(100)
		sc.addProduct(100)
		let resp = discount.calc(sc.products)
		expect(resp.toFixed(2)).to.equal('0.15')
	})
})

es6 实现

class ShoppingCart {
	constructor() {
		this.products = []
	}

	addProduct(p) {
		this.products.push(p)
	}
}

class Discount {
	calc(products) {
		let ndiscount = new NumberDiscount()
		let pdiscount = new PriceDiscount()
		let none = new NoneDiscount()
		ndiscount.setNext(pdiscount)
		pdiscount.setNext(none)
		return ndiscount.exec(products)
	}
}

class NumberDiscount {
	constructor() {
		this.next = null
	}

	setNext(fn) {
		this.next = fn
	}

	exec(products) {
		let result = 0
		if (products.length > 3) result = 0.05

		return result + this.next.exec(products)
	}
}

class PriceDiscount {
	constructor() {
		this.next = null
	}

	setNext(fn) {
		this.next = fn
	}

	exec(products) {
		let result = 0
		let total = products.reduce((a, b) => a + b)

		if (total >= 500) result = 0.1

		return result + this.next.exec(products)
	}
}

class NoneDiscount {
	exec() {
		return 0
	}
}

export { ShoppingCart, Discount }

const expect = require('chai').expect
import { ShoppingCart, Discount } from '../src/behavioral/chain-of-resp/chain-of-resp-es6'

describe('责任链模式 es6测试', () => {
	it('购物车金额 > $500', () => {
		const discount = new Discount()
		const sc = new ShoppingCart()
		sc.addProduct(1000)
		let resp = discount.calc(sc.products)

		expect(resp).to.equal(0.1)
	})
	it('大于三个商品', () => {
		const discount = new Discount()
		const sc = new ShoppingCart()
		sc.addProduct(100)
		sc.addProduct(100)
		sc.addProduct(100)
		sc.addProduct(100)
		let resp = discount.calc(sc.products)
		expect(resp).to.equal(0.05)
	})
	it('大于三个商品并且 >$500', () => {
		const discount = new Discount()
		const sc = new ShoppingCart()
		sc.addProduct(1000)
		sc.addProduct(100)
		sc.addProduct(100)
		sc.addProduct(100)
		let resp = discount.calc(sc.products)
		expect(resp.toFixed(2)).to.equal('0.15')
	})
})