vue自定义指令VNode详解

1、自定义指令钩子函数

Vue.directive('my-directive', {
  bind: function () {
    // 做绑定的准备工作
    // 比如添加事件监听器,或是其他只需要执行一次的复杂操作
  },
  inserted: function (newValue, oldValue) {
    // 被绑定元素插入父节点时调用
  },
  update: function (newValue, oldValue) {
    // 根据获得的新值执行对应的更新
    // 对于初始值也会被调用一次
  },
  unbind: function () {
    // 做清理工作
    // 比如移除在 bind() 中添加的事件监听器
  }
})

指令定义函数提供了几个钩子函数(可选):

  • bind: 只调用一次,指令第一次绑定到元素时调用,用这个钩子函数可以定义一个在绑定时执行一次的初始化动作。
  • inserted: 被绑定元素插入父节点时调用(父节点存在即可调用,不必存在于 document 中)。
  • update: 所在组件的 VNode 更新时调用,但是可能发生在其孩子的 VNode 更新之前。指令的值可能发生了改变也可能没有。但是你可以通过比较更新前后的值来忽略不必要的模板更新 (详细的钩子函数参数见下)。
  • componentUpdated: 所在组件的 VNode 及其孩子的 VNode 全部更新时调用。
  • unbind: 只调用一次, 指令与元素解绑时调用。
    接下来我们来看一下钩子函数的参数 (包括 el,binding,vnode,oldVnode) 。

2、钩子函数参数

钩子函数被赋予了以下参数:

  • el: 指令所绑定的元素,可以用来直接操作 DOM 。
  • binding: 一个对象,包含以下属性:
    • name: 指令名,不包括 v- 前缀。
    • value: 指令的绑定值, 例如: v-my-directive=”1 + 1”, value 的值是 2。
    • oldValue: 指令绑定的前一个值,仅在 update 和 componentUpdated 钩子中可用。无论值是否改变都可用。
    • expression: 绑定值的字符串形式。 例如 v-my-directive=”1 + 1” , expression 的值是 “1 + 1”。
    • arg: 传给指令的参数。例如 v-my-directive:foo, arg 的值是 “foo”。
      modifiers: 一个包含修饰符的对象。 例如: v-my-directive.foo.bar, 修饰符对象 modifiers 的值是 { foo: true, bar: true }。
  • vnode: Vue 编译生成的虚拟节点
  • oldVnode: 上一个虚拟节点,仅在 update 和 componentUpdated 钩子中可用。

3、VNode接口

export default class VNode {
  tag: string | void;
  data: VNodeData | void;
  children: ?Array;
  text: string | void;
  elm: Node | void;
  ns: string | void;
  context: Component | void; // rendered in this component's scope
  functionalContext: Component | void; // only for functional component root nodes
  key: string | number | void;
  componentOptions: VNodeComponentOptions | void;
  componentInstance: Component | void; // component instance
  parent: VNode | void; // component placeholder node
  raw: boolean; // contains raw HTML? (server only)
  isStatic: boolean; // hoisted static node
  isRootInsert: boolean; // necessary for enter transition check
  isComment: boolean; // empty comment placeholder?
  isCloned: boolean; // is a cloned node?
  isOnce: boolean; // is a v-once node?
  asyncFactory: Function | void; // async component factory function
  asyncMeta: Object | void;
  isAsyncPlaceholder: boolean;
  ssrContext: Object | void;

  constructor (
    tag?: string,
    data?: VNodeData,
    children?: ?Array,
    text?: string,
    elm?: Node,
    context?: Component,
    componentOptions?: VNodeComponentOptions,
    asyncFactory?: Function
  ) {
    this.tag = tag
    this.data = data
    this.children = children
    this.text = text
    this.elm = elm
    this.ns = undefined
    this.context = context
    this.functionalContext = undefined
    this.key = data && data.key
    this.componentOptions = componentOptions
    this.componentInstance = undefined
    this.parent = undefined
    this.raw = false
    this.isStatic = false
    this.isRootInsert = true
    this.isComment = false
    this.isCloned = false
    this.isOnce = false
    this.asyncFactory = asyncFactory
    this.asyncMeta = undefined
    this.isAsyncPlaceholder = false
  }

  // DEPRECATED: alias for componentInstance for backwards compat.
  /* istanbul ignore next */
  get child (): Component | void {
    return this.componentInstance
  }
}

export const createEmptyVNode = (text: string = '') => {
  const node = new VNode()
  node.text = text
  node.isComment = true
  return node
}

export function createTextVNode (val: string | number) {
  return new VNode(undefined, undefined, undefined, String(val))
}

// optimized shallow clone
// used for static nodes and slot nodes because they may be reused across
// multiple renders, cloning them avoids errors when DOM manipulations rely
// on their elm reference.
export function cloneVNode (vnode: VNode, deep?: boolean): VNode {
  const cloned = new VNode(
    vnode.tag,
    vnode.data,
    vnode.children,
    vnode.text,
    vnode.elm,
    vnode.context,
    vnode.componentOptions,
    vnode.asyncFactory
  )
  cloned.ns = vnode.ns
  cloned.isStatic = vnode.isStatic
  cloned.key = vnode.key
  cloned.isComment = vnode.isComment
  cloned.isCloned = true
  if (deep && vnode.children) {
    cloned.children = cloneVNodes(vnode.children)
  }
  return cloned
}

export function cloneVNodes (vnodes: Array, deep?: boolean): Array<VNode> {
  const len = vnodes.length
  const res = new Array(len)
  for (let i = 0; i < len; i++) {
    res[i] = cloneVNode(vnodes[i], deep)
  }
  return res
}

4、VNode

不存在父节点:

vue自定义指令VNode详解_第1张图片

存在父节点:

vue自定义指令VNode详解_第2张图片

v-IME自定义指令示例:

import { log } from 'SUtil'
const install = Vue => {
  let isBind = true
  let IMEService = ''
  let $this = new Vue({
    data () {
      return {
        outEl: null,
        outVnode: null
      }
    },
    watch: {
      outVnode (value, oldValue) {
        if (oldValue) {
          oldValue.componentInstance.isFocus = false
        }
      }
    }
  })
  async function openIme (e, option) {
    log.d('openIme', isBind, $this.$data.outVnode.componentInstance.percentValue)
    if ($this.$data.outEl && IMEService && isBind) {
      log.d('open')
      $this.$data.outEl.target.focus()
      let ret = await IMEService.open({
        type: IMEService[option.type],
        track: Number.parseInt(option.track),
        w: Number.parseInt(option.w),
        h: Number.parseInt(option.h),
        x: Number.parseInt(option.x),
        y: Number.parseInt(option.y)
      })
      if (ret.isSuccess) {
        console.log('输入法开启成功')
      }
    }
  }
  async function closeIme (e) {
    log.d('closeIme', isBind, $this.$data.outVnode.componentInstance.percentValue)
    if ($this.$data.outEl && IMEService && isBind) {
      log.d('close')
      $this.$data.outVnode.componentInstance.isFocus = false
      let ret = await IMEService.close()
      if (ret.isSuccess) {
        console.log('输入法关闭成功')
      }
    }
  }
  Vue.directive('IME', {
    bind: function (el, binding, vnode) {
      $this.$data.outVnode = vnode
      if (window.taf && window.taf.service.IMEService) {
        IMEService = window.taf.service.IMEService
      } else {
        log.e('IMEService 不存在')
        $this.$data.outVnode.componentInstance.$emit('error', '输入法故障')
        log.d('error', $this.$data.outVnode.componentInstance.percentValue)
      }
    },
    inserted: function (el, binding, vnode) {
      const inputDom = vnode.componentInstance.$el.querySelector('input')
      if (inputDom) {
        inputDom.addEventListener('focus', async focusEvent => {
          log.d('focus')
          $this.$data.outEl = focusEvent
          $this.$data.outVnode = vnode
          vnode.componentInstance.ctrlBlur = true
          openIme(focusEvent, binding.value)
        })
        inputDom.addEventListener('click', async focusEvent => {
          log.d('click')
          $this.$data.outEl = focusEvent
          $this.$data.outVnode = vnode
          vnode.componentInstance.ctrlBlur = true
          openIme(focusEvent, binding.value)
        })
        inputDom.addEventListener('blur', async focusEvent => {
          log.d('blur')
          $this.$data.outEl = focusEvent
          $this.$data.outVnode = vnode
          vnode.componentInstance.ctrlBlur = false
          closeIme(focusEvent)
        })
      }
      isBind = true
    },
    async unbind (el, binding, vnode) {
      log.d('unbind')
      if (window.taf && window.taf.service.IMEService) {
        IMEService = window.taf.service.IMEService
      } else {
        log.e('IMEService 不存在')
        $this.$data.outVnode.componentInstance.$emit('error', 'IMEService 不存在')
        log.d('error', $this.$data.outVnode.componentInstance.percentValue)
      }
      const inputDom = vnode.componentInstance.$el.querySelector('input')
      if (inputDom) {
        inputDom.removeEventListener('click', openIme)
        isBind = false
        await IMEService.close()
      }
    }
  })
}
export default {
  install
}

你可能感兴趣的:(vue,vue,vue自定义指令,VNode)