Слушать события от динамических компонентов vue

Vue.component("button-counter", {
  data: function() {
    return {
      count: this.initial_count
    }
  },
  props: ['initial_count'],
  methods: {
    add: function() {
      this.count++
        this.$emit('myevent', this.count)
    }
  },
  template: '<button v-on:click = "add">You clicked me {{ count }} times.</button>'
})

let app = new Vue({
  el: "#app",
  data() {
    return {
      initial_count: 10,
    }
  },
  mounted: function() {
    let initial_count = this.initial_count

    let ButtonCounterComponentClass = Vue.extend({
      data: function() {
        return {}
      },
      render(h) {
        return h("button-counter", {
          props: {
            initial_count: initial_count
          },
          // **** Added this ****
          on: {
            myevent: count => {
              this.$emit('myevent', count);
            }
          }
          // ****
        })
      }
    })
    let button_counter_instance = new ButtonCounterComponentClass()
    button_counter_instance.$mount()
    // **** Changed the next line ****
    button_counter_instance.$on('myevent', count => {
      console.info('listened!')
      this.say(count)
    })
    this.$refs.container.appendChild(button_counter_instance.$el)
  },
  methods: {
    say: function(message) {
      alert(message)
    }
  }
})

<script src = "https://cdn.jsdelivr.net/npm/[email protected]/dist/vue.js"></script>

<div id = "app">
    <button-counter initial_count=20 v-on:myevent = "say"></button-counter>
    <div ref='container'></div>
</div>