职责链模式在项目中的运用

  /**
   * 职责链模式
   */
  export class Chain {
    constructor(fn) {
      this.fn = fn
      this.successor = null
    }
  
    setNextSuccessor(successor) {
      return (this.successor = successor)
    }
  
    async passRequest() {
      const res = await this.fn.apply(this, arguments)
      if (res === 'nextSuccessor' && this.successor) {
        return await this.successor.passRequest.apply(this.successor, arguments)
      }
      return res
    }
  }

  /**
   * 使用职责链模式进行保存前的校验
   * @param {Object} data 需要校验的数据
   */
  async function validate(data) {
    // 校验：小计金额最大值限制
    function validateAmountMax() {
      const index = data.findIndex((item) => item.Amount >= 99999999)
      if (index > -1) {
        return new Promise((resolve) => {
          const modal = Modal.confirm({
            title: '提示',
            content: '小计金额不能超过99999999',
            icon: createVNode(ExclamationCircleOutlined),
            okText: '确定',
            cancelText: createVNode(),
            async onOk() {
              nextTick(() => modal.destroy())
              resolve(false)
            }
          })
        })
      }
      return 'nextSuccessor'
    }

    // 校验：采购价格是否高于加权平均价
    function validateInPriceHigherThanAutoPrice() {
      // 判断采购设置中是否启用了：“采购价格高于加权平均价时，进行提示”，如果启用了，
      // 当存在某一商品的采购价格高于加权平均价时，弹框提示
      if (purchaseSettings.value.InPriceHigherThanAutoPrice == 'Y') {
        const needTip = data.some((item) => item.Price > item.CostPrice)
        
        if (needTip) {
          return new Promise((resolve) => {
            const modal = Modal.confirm({
              title: '确认',
              content: '存在商品的当前价格高于加权平均价，是否继续保存？',
              icon: createVNode(ExclamationCircleOutlined),
              okText: '确定',
              cancelText: '取消',
              async onOk() {
                nextTick(() => modal.destroy())
                resolve('nextSuccessor')
              },
              async onCancel() {
                nextTick(() => modal.destroy())
                resolve(false)
              }
            })
          })
        }
      }
      return 'nextSuccessor'
    }

    // 校验：生鲜商品允许价格高于商品档案进价
    function validateFreshAllowInPriceHigherThanItemPrice() {
      // 采购设置中不启用：“生鲜商品允许价格高于商品档案进价”，那么当一个商品为生鲜商品，
      // 且价格高于档案进价时，弹框提示
      if (purchaseSettings.value.FreshAllowInPriceHigherThanItemPrice == 'N') {
        const needTip = data.some((item) => item.IsFresh && item.Price > item.PurcPrice)
        if (needTip) {
          return new Promise((resolve) => {
            const modal = Modal.confirm({
              title: '提示',
              content: '采购设置设置了不允许生鲜商品价格高于商品档案进价，请重新输入价格！',
              icon: createVNode(ExclamationCircleOutlined),
              okText: '确定',
              cancelText: createVNode(),
              async onOk() {
                nextTick(() => modal.destroy())
                resolve(false)
              }
            })
          })
        }
      }
      return true
    }

    // 将三个校验函数包装成职责链节点
    const valAmount = new Chain(validateAmountMax)
    const valCostPrice = new Chain(validateInPriceHigherThanAutoPrice)
    const valFresh = new Chain(validateFreshAllowInPriceHigherThanItemPrice)
    // 指定节点在职责链中的顺序
    valAmount.setNextSuccessor(valCostPrice).setNextSuccessor(valFresh)
    // 把请求传递给第一个节点
    return await valAmount.passRequest()
  }

  // 保存
  async function save(data) {
    if (!(await validate(data))) return false

    // ....... 调接口进行保存
  }