Element el-checkbox-group v-model不支持对象(object)解决方案

<template>
  <div id="app">
    <el-checkbox :indeterminate="isIndeterminate" v-model="checkAll" @change="handleCheckAllChange">全选</el-checkbox>
    <div style="margin: 15px 0;"></div>
    <el-checkbox-group v-model="checkedCities" @change="handleCheckedCitiesChange">
      <el-checkbox v-for="city in cities" :label="city.id" :key="city.id">{{city.name}}</el-checkbox>
    </el-checkbox-group>
  </div>
</template>
<script>
export default {
  name: 'Demo',
  components: {
  },
  data () {
    return {
      checkAll: false,
      checkedCities: [],
      cities: [
        { id: 1, name: '北京' },
        { id: 2, name: '上海' },
        { id: 3, name: '广州' },
        { id: 4, name: '深圳' },
        { id: 5, name: '杭州' }
      ],
      isIndeterminate: true
    }
  },
  computed: {
    // 选中的对象数组
    checkedObj () {
      return this.cities.filter(
          option => this.checkedCities.some(
              checked => checked === option.id
          )
      )
    }
  },
  watch: {
    checkedObj: {
      handler (val) {
        console.log(val)
      },
      deep: true,
      immediate: true
    }
  },
  methods: {
    // 全选
    handleCheckAllChange(val) {
      this.checkedCities = val ? this.cities.map(item => item.id) : []
      this.isIndeterminate = false
    },
    // 选择
    handleCheckedCitiesChange(value) {
      let checkedCount = value.length
      this.checkAll = checkedCount === this.cities.length
      this.isIndeterminate = checkedCount > 0 && checkedCount < this.cities.length
    }
  }
}
</script>

git clone https://github.com/ElemeFE/element.git

return this.model.indexOf(this.label) > -1 || JSON.stringify(this.model).indexOf(JSON.stringify(this.label)) > -1