vue中父组件向子组件传值问题

问题：当父组件传值给子组件echarts时，发现子组件获取的props为空，刚开始以为是钩子函数放错了地方，后来发现从mounted和created都不行。当在父组件data定义传递的数据的时候子组件显示正常

原因：后来经过排查，此处省略N字，发现echarts是在渲染的时候就传递数据

解决方案：在父组件定义一个flag，当数据获得的之后再进行子组件的渲染

//父组件
   <div class="chart-wrapper">
    <pie-chart v-if="flag" :pie-data="piedata"></pie-chart>
  </div>
  ...
  import {getPie} from '@/api/status'
  export default {
  name: 'device',
  data() {
    return {
      flag:false,
      piedata:{},
      ...
  },
  created(){
    this.init()
  },
 methods:{
   init(){
        getPie().then(this.getInfoSucc)
   },
   getInfoSucc(res){
      res = res.data;
       if(res.code ==0){
         const values = res.values;
         this.piedata = values.piedata;
         this.flag = true
       }
     }

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 https://blog.csdn.net/Uookic/article/details/80638883?utm_source=copy

　　

//子组件
<template>
  <div :class="className" :style="{height:height,width:width}"></div>
</template>

<script>
import echarts from 'echarts'
require('echarts/theme/macarons') // echarts theme
import { debounce } from '@/utils'

export default {
  props: {
    pieData: {
      type: Object
    },
    msg: {
      type:Number
    },
    className: {
      type: String,
      default: 'chart'
    },
    width: {
      type: String,
      default: '100%'
    },
    height: {
      type: String,
      default: '300px'
    }
  },
  data() {
    return {
      chart: null
    }
  },
  // watch: {
  //   piedata: {
  //     deep: true,
  //     handler(val) {
  //       console.log(val)
  //       this.setOptions(val)
  //     }
  //   }
  // },
  mounted() {
    console.log("pieData:"+JSON.stringify(this.pieData))
    this.initChart()
    this.__resizeHanlder = debounce(() => {
      if (this.chart) {
        this.chart.resize()
      }
    }, 100)
    window.addEventListener('resize', this.__resizeHanlder)
  },
  beforeDestroy() {
    if (!this.chart) {
      return
    }
    window.removeEventListener('resize', this.__resizeHanlder)
    this.chart.dispose()
    this.chart = null
  },
  methods: {
    setOptions({ text, arrtype, arrdata } = {}) {
      this.chart.setOption({
        title: {
          text: text
        },
        tooltip: {
          trigger: 'item',
          formatter: '{a} <br/>{b} : {c} ({d}%)'
        },
        legend: {
          left: 'center',
          bottom: '10',
          data: arrtype
        },
        calculable: true,
        series: [
          {
            name: '',
            type: 'pie',
            roseType: 'radius',
            radius: [15, 95],
            center: ['50%', '42%'],
            data: arrdata,
            animationEasing: 'cubicInOut',
            animationDuration: 2600
          }
        ]
      })
    },
    initChart() {
      this.chart = echarts.init(this.$el, 'macarons')
      this.setOptions(this.pieData);
    }
  }
}
</script>

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https://blog.csdn.net/Uookic/article/details/80638883?utm_source=copy