vue 在2.0已经去除了dispatch 和brocast，但是又想用它的特性怎么办?

1 初级版,只能传一个参数

问题:为什么不用eventBus?如果想要用类似的功能独立于业务项目，不可能在一个项目用一次，就要改一下代码，用eventBus.
实现原理:假设s.vue要向app.vue发消息，通过options.name的方式找到目标组件target，然后target.$emit(target, eventName, params)自己触发事件.
核心实现(如下:),可以通过mixins的方式混入。
dispatch('$option.name','事件名', 参数)

// emmiter.js
function broadcast (componentName, eventName, data) {
  this.$children.forEach(child => {
    if (child.$options.name === componentName) {
      child.$emit.call(child, eventName, data)
    } else {
      broadcast.call(child, componentName, eventName, data)
    }
  })
}
export default {
  methods: {
    dispatch (componentName, eventName, data) {
      let parent = this.$parent || this.$root
      let name = parent.$options.name
      while (parent && (!name || parent.$options.name !== componentName)) {
        parent = parent.$parent
        if (parent) {
          name = parent.$options.name
        }
      }
      console.log(parent)
      parent.$emit.apply(parent, [eventName].concat(data))
    },
    broadcast (componentName, eventName, data) {
      broadcast.call(this ,componentName, eventName, data)
    }
  }
}

具体例子:

// app.vue
<template>
  <div id="app">
    <input type="text" v-model="rMsg"><button @click="huixin">回信</button>
    <div>hello</div>
    <grand></grand>
  </div>
</template>
<script>
import grand from './components/g'
import emitter from './components/emmit'
export default {
  mixins: [emitter],
  name: 'app',
  data () {
    return {
      show: false,
      rMsg: 'sb我收到信息了，考上大学你也找不到工作，还得你爹给你买房！'
    }
  },
  methods: {
    fn (e){
      console.log('消息收到了', e)
    },
    huixin () {
      this.broadcast('son', 'huixin', this.rMsg)
    }
  },
  mounted () {
    this.$on('joy', this.fn)
  },
  components: {
    grand
  }
}
</script>

// g.vue
<template>
  <div>
    我是grand,中文就是爷爷的意识，现在组件建好了，要干大事咯
    <father></father>
  </div>
</template>
<script>
import father from './f'
export default {
  name: 'grand',
  components: {
    father
  }
}
</script>

// f.vue
<template>
  <div>
    我是father,并且我有一个son
    <son></son>
  </div>
</template>
<script>
import son from './s'
export default {
  name: 'father',
  components: { son }
}
</script>

// s.vue
<template>
  <div>
    我是son
    <el-form label-width="100px">
      <el-form-item label="喜事">
        <el-input v-model="joyText" style="width: 240px;"></el-input>
      </el-form-item>
    </el-form>
    <el-button @click="transferJoy">向app报喜</el-button>
  </div>
</template>
<script>
import emitter from './emmit'
export default {
  mixins: [emitter],
  name: 'son',
  data () {
    return {
      joyText: '考上清华大学长河分校'
    }
  },
  created () {
    this.$on('huixin', (data) => {
      console.log('回信', data)
    })
  },
  methods: {
    transferJoy () {
      this.dispatch('app', 'joy', this.joyText)
    }
  }
}
</script>

最终效果:

运行效果

2 源码实现:

// 所有的父组件都自己触发事件，自己监听
 Vue.prototype.$dispatch = function (event) {
    var shouldPropagate = this.$emit.apply(this, arguments)
    if (!shouldPropagate) return
    var parent = this.$parent
    var args = toArray(arguments)
    // use object event to indicate non-source emit
    // on parents
    args[0] = { name: event, source: this }
    while (parent) {
      shouldPropagate = parent.$emit.apply(parent, args)
      parent = shouldPropagate
        ? parent.$parent
        : null
    }
    return this
  }
// 所有的子组件自己触发事件
  Vue.prototype.$broadcast = function (event) {
    var isSource = typeof event === 'string'
    event = isSource
      ? event
      : event.name
    // if no child has registered for this event,
    // then there's no need to broadcast.
    if (!this._eventsCount[event]) return
    var children = this.$children
    var args = toArray(arguments)
    if (isSource) {
      // use object event to indicate non-source emit
      // on children
      args[0] = { name: event, source: this }
    }
    for (var i = 0, l = children.length; i < l; i++) {
      var child = children[i]
      var shouldPropagate = child.$emit.apply(child, args)
      if (shouldPropagate) {
        child.$broadcast.apply(child, args)
      }
    }
    return this
  }