职责链模式

[txw2018]

定义： 为解除请求的发送者和接收者之间耦合，而使多个对象都有机会处理这个请求。将这些对象连成一条链，并沿着这条链传递该请求，直到有一个对象处理它

下面模拟购物车提交订单流程

const UI = {
  Alert(options) {
    const msg = options.msg || '您确定吗'
    return new Promise((resolve, reject) => {
      var r = confirm(msg)
      if (r) {
        resolve(true)
      } else {
        reject(false)
      }
    })
  }
}

const validateHandler = {
  validateAddress() {
    if (true) {
      UI.Alert({
        msg: "您确定地址正确吗"
      })
      .then(() => {
        console.log(1111)
        this.next()
      })
      .catch(err => {
      })
    }
    return false
  },
  validateMoney() {
    if (true) {
      UI.Alert({
        msg: "您确定继续支付吗"
      })
      .then(() => {
        console.log(2222)
        this.next()
      })
      .catch(err => {
      })

    }
    return false
  },
  validateCoupon() {
    if (true) {
      console.log(3333)
      return true
    }
    return false
  }
}
class Chain {
  constructor(fn) {
    this.fn = fn
    this.sucessor = null
  }
  setNext(fnc) {
    this.sucessor = fnc
    return fnc
  }
  next() {
    this.sucessor.run.apply(this.sucessor, arguments)
  }
  run() {
    const result = this.fn.apply(this, arguments)
    if (result) {
      this.next()
    }
  }
}
const validateObj = {}

const validateArr = Object.keys(validateHandler)


for (const fnc of validateArr) { // 循环执行验证方法
  validateObj[fnc + 'Chain'] = new Chain(validateHandler[fnc])
}

const {
  validateAddressChain,
  validateMoneyChain,
  validateCouponChain
} = validateObj


validateAddressChain
  .setNext(validateMoneyChain)
  .setNext(validateCouponChain)

validateAddressChain.run()