状态模式(behavioral 8)

3.8 状态模式(state)

• 允许对象在内部状态发生改变时改变它的行为，对象看起来好像修改了它的类。
  • 我们创建表示各种状态的对象和一个行为随着状态对象改变而改变的 context 对象。

// 一个行为随着状态改变而改变的context对象
function Order() {
	this.state = new WaitingForPayment()

	this.nextState = function () {
		this.state = this.state.next()
	}
}
//创建各种状态的对象
function WaitingForPayment() {
	this.name = 'waitingForPayment'
	this.next = function () {
		return new Shipping()
	}
}

function Shipping() {
	this.name = 'shipping'
	this.next = function () {
		return new Delivered()
	}
}

function Delivered() {
	this.name = 'delivered'
	this.next = function () {
		return this
	}
}

module.exports = Order

const expect = require('chai').expect
const Order = require('../src/behavioral/state/state')

describe('状态模式 测试', () => {
	it('订单', () => {
		var order = new Order()
		expect(order.state.name).to.equal('waitingForPayment')
		order.nextState()
		expect(order.state.name).to.equal('shipping')
		order.nextState()
		expect(order.state.name).to.equal('delivered')
	})
})

es6 实现

// 一个行为随着状态改变而改变的context对象
class Order {
	constructor() {
		this.state = new WaitingForPayment()
	}
	nextState() {
		this.state = this.state.next()
	}
}

// 抽象类
class OrderStatus {
	constructor(name, nextStatus) {
		this.name = name
		this.nextStatus = nextStatus
	}
	next() {
		return new this.nextStatus()
	}
}

//创建各种状态的对象
class WaitingForPayment extends OrderStatus {
	constructor() {
		super('waitingForPayment', Shipping)
	}
}
class Shipping extends OrderStatus {
	constructor() {
		super('shipping', Delivered)
	}
}
class Delivered extends OrderStatus {
	constructor() {
		super('delivered', Delivered)
	}
}

export { Order }

const expect = require('chai').expect
import { Order } from '../src/behavioral/state/state_es6'

describe('状态模式 es6测试', () => {
	it('订单', () => {
		var order = new Order()
		expect(order.state.name).to.equal('waitingForPayment')
		order.nextState()
		expect(order.state.name).to.equal('shipping')
		order.nextState()
		expect(order.state.name).to.equal('delivered')
	})
})