vue 对象添加或删除成员时无法实时更新的解决方法

this.$set(this.age,'age',18);
this.$delete(this.age,'age');

let vm = new Vue({
  el : '#app',
  data : {
    age:{}
  }
});
Vue.set(vm.age,'age',18);
Vue.delete(vm.age,'age');

<style lang="sass">

</style>
<template>
<div>
  <div>
    <div>

    </div>
  </div>
</div>
</template>
<script>
  export default {
    data(){
      return {

      }
    },
    methods: {
      ceshi(){

      }
    }
  }
</script>

</style>
<template>
<div>
  <div>
    <div>
      <div v-for="item in items">
        <span>{{ item }}</span>
      </div>
      <button @click="ceshi">anniu</button>
    </div>
  </div>
</div>
</template>

<script>
  export default {
    data(){
      return {
        items: [11,22],
        obj: { a: 'aa', b: 'bb' }
      }
    },
    methods: {
      ceshi(){
        this.items[2] = 33; // 这样的写法数据是无法重新渲染的
      }
    }
  }
</script>

methods: {
  ceshi(){
    this.$set(this.items, 2, 33)
  }
},

<div v-for="item in items">
 <span v-for="(i, j) in item">{{ i }}--{{ j }}</span>
</div>

this.items[0] = Object.assign({}, this.items[0], { b: '22' });
this.$set(this.items, 0, this.items[0]);

<template>
  <div>
    <div v-for="item in obj">
     <span>{{ item }}</span>
    </div>
  </div>
</template>

data(){
  return {
    obj: { a: 'aa', b: 'bb' }
  }
}

methods: {
  ceshi(){
    this.obj['c'] = '000'; // 不起作用
    this.$set(this.obj, 'c', '000'); //起作用 
  }
},