<div id='app'>
  <input type="text" v-model="inputValue" v-focus>
</div>
<script>
  Vue.directive('focus', {
    // 第一次綁定元素時(shí)調(diào)用
    bind () {
      console.log('bind')
    },
    // 當(dāng)被綁定的元素插入到 DOM 中時(shí)……
    inserted: function (el) {
      console.log('inserted')
      el.focus()
    },
    // 所在組件VNode發(fā)生更新時(shí)調(diào)用
    update () {
      console.log('update')
    },
    // 指令所在組件的 VNode 及其子 VNode 全部更新后調(diào)用
    componentUpdated () {
      console.log('componentUpdated')
    },
    // 只調(diào)用一次，指令與元素解綁時(shí)調(diào)用
    unbind () {
      console.log('unbind')
    }
  })
  new Vue({
    data: {
      inputValue: ''
    }
  }).$mount('#app')
</script>

// src/core/vdom/patch.js
const hooks = ['create', 'activate', 'update', 'remove', 'destroy']
export function createPatchFunction (backend) {
  let i, j
  const cbs = {}

  const { modules, nodeOps } = backend
  for (i = 0; i < hooks.length; ++i) {
    cbs[hooks[i]] = []
    // modules對應(yīng)vue中模塊，具體有class, style, domListener, domProps, attrs, directive, ref, transition
    for (j = 0; j < modules.length; ++j) {
      if (isDef(modules[j][hooks[i]])) {
        // 最終將hooks轉(zhuǎn)換為{hookEvent: [cb1, cb2 ...], ...}形式
        cbs[hooks[i]].push(modules[j][hooks[i]])
      }
    }
  }
  // ....
  return function patch (oldVnode, vnode, hydrating, removeOnly) {
    // ...
  }
}

{
  tag: 'input',
  parent: ASTElement,
  directives: [
    {
      arg: null, // 參數(shù)
      end: 56, // 指令結(jié)束字符位置
      isDynamicArg: false, // 動態(tài)參數(shù),v-xxx[dynamicParams]='xxx'形式調(diào)用
      modifiers: undefined, // 指令修飾符
      name: "model",
      rawName: "v-model", // 指令名稱
      start: 36, // 指令開始字符位置
      value: "inputValue" // 模板
    },
    {
      arg: null,
      end: 67,
      isDynamicArg: false,
      modifiers: undefined,
      name: "focus",
      rawName: "v-focus",
      start: 57,
      value: ""
    }
  ],
  // ...
}

with (this) {
    return _c('div', {
        attrs: {
            "id": "app"
        }
    }, [_c('input', {
        directives: [{
            name: "model",
            rawName: "v-model",
            value: (inputValue),
            expression: "inputValue"
        }, {
            name: "focus",
            rawName: "v-focus"
        }],
        attrs: {
            "type": "text"
        },
        domProps: {
            "value": (inputValue) // 處理v-model指令時(shí)添加的屬性
        },
        on: {
            "input": function($event) { // 處理v-model指令時(shí)添加的自定義事件
                if ($event.target.composing)
                    return;
                inputValue = $event.target.value
            }
        }
    })])
}

// src/core/vdom/patch.js
function createElm (
    vnode,
    insertedVnodeQueue,
    parentElm,
    refElm,
    nested,
    ownerArray,
    index
  ) {
    // ...
    // createComponent有返回值，是創(chuàng)建組件的方法，沒有返回值，則繼續(xù)走下面的方法
    if (createComponent(vnode, insertedVnodeQueue, parentElm, refElm)) {
      return
    }

    const data = vnode.data
    // ....
    if (isDef(data)) {
        // 真實(shí)節(jié)點(diǎn)創(chuàng)建之后，更新節(jié)點(diǎn)屬性，包括指令
        // 指令首次會調(diào)用bind方法，然后會初始化指令后續(xù)hooks方法
        invokeCreateHooks(vnode, insertedVnodeQueue)
    }
    // 從底向上，依次插入
    insert(parentElm, vnode.elm, refElm)
    // ...
  }

// src/core/vdom/modules/directives.js

// 默認(rèn)拋出的都是updateDirectives方法
export default {
  create: updateDirectives,
  update: updateDirectives,
  destroy: function unbindDirectives (vnode: VNodeWithData) {
    // 銷毀時(shí)，vnode === emptyNode
    updateDirectives(vnode, emptyNode)
  }
}

function updateDirectives (oldVnode: VNodeWithData, vnode: VNodeWithData) {
  if (oldVnode.data.directives || vnode.data.directives) {
    _update(oldVnode, vnode)
  }
}

function _update (oldVnode, vnode) {
  const isCreate = oldVnode === emptyNode
  const isDestroy = vnode === emptyNode
  const oldDirs = normalizeDirectives(oldVnode.data.directives, oldVnode.context)
  const newDirs = normalizeDirectives(vnode.data.directives, vnode.context)
  // 插入后的回調(diào)
  const dirsWithInsert = [
  // 更新完成后回調(diào)
  const dirsWithPostpatch = []

  let key, oldDir, dir
  for (key in newDirs) {
    oldDir = oldDirs[key]
    dir = newDirs[key]
    // 新元素指令，會執(zhí)行一次inserted鉤子方法
    if (!oldDir) {
      // new directive, bind
      callHook(dir, 'bind', vnode, oldVnode)
      if (dir.def && dir.def.inserted) {
        dirsWithInsert.push(dir)
      }
    } else {
      // existing directive, update
      // 已經(jīng)存在元素，會執(zhí)行一次componentUpdated鉤子方法
      dir.oldValue = oldDir.value
      dir.oldArg = oldDir.arg
      callHook(dir, 'update', vnode, oldVnode)
      if (dir.def && dir.def.componentUpdated) {
        dirsWithPostpatch.push(dir)
      }
    }
  }

  if (dirsWithInsert.length) {
    // 真實(shí)DOM插入到頁面中，會調(diào)用此回調(diào)方法
    const callInsert = () => {
      for (let i = 0; i < dirsWithInsert.length; i++) {
        callHook(dirsWithInsert[i], 'inserted', vnode, oldVnode)
      }
    }
    // VNode合并insert hooks
    if (isCreate) {
      mergeVNodeHook(vnode, 'insert', callInsert)
    } else {
      callInsert()
    }
  }

  if (dirsWithPostpatch.length) {
    mergeVNodeHook(vnode, 'postpatch', () => {
      for (let i = 0; i < dirsWithPostpatch.length; i++) {
        callHook(dirsWithPostpatch[i], 'componentUpdated', vnode, oldVnode)
      }
    })
  }

  if (!isCreate) {
    for (key in oldDirs) {
      if (!newDirs[key]) {
        // no longer present, unbind
        callHook(oldDirs[key], 'unbind', oldVnode, oldVnode, isDestroy)
      }
    }
  }
}

// src/core/vdom/patch.js
function patchVnode (
    oldVnode,
    vnode,
    insertedVnodeQueue,
    ownerArray,
    index,
    removeOnly
  ) {
    // ...
    const oldCh = oldVnode.children
    const ch = vnode.children
    // 全量更新節(jié)點(diǎn)的屬性
    if (isDef(data) && isPatchable(vnode)) {
      for (i = 0; i < cbs.update.length; ++i) cbs.update[i](oldVnode, vnode)
      if (isDef(i = data.hook) && isDef(i = i.update)) i(oldVnode, vnode)
    }
    // ...
    if (isDef(data)) {
    // 調(diào)用postpatch鉤子
      if (isDef(i = data.hook) && isDef(i = i.postpatch)) i(oldVnode, vnode)
    }
  }