vue父组件异步传递prop到子组件echarts画图问题踩坑总结
Posted goloving
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效果图：
大致思路：考虑到5张图都是折线图，所以准备用一个子组件承接echarts画图，然后父组件通过prop传递不同数据来展示不同的图
踩坑问题：
1、引入line子组件，画了5个元素，但是只显示一个
原因：id重复
解决方案：prop传递不同id名
2、父组件传递的数据在子组件报错
这里情况比较特殊，我用父组件数据data里面给demo数据的时候，子组件是拿得到数据的，图片正常显示，所以以为可以了，当换成从后台请求的数据后，发现子组件总是报错，data.count is not a function ，在子组件的mounted里面打印父组件传递过来的prop，发现是空数组。
刚开始我以为是mounted生命周期的问题，所以改成created阶段去请求后台数据，然后传递给子组件，发现仍然不行。
这时，我给父组件数据加上默认一些demo数据，然后再created阶段再去请求后台数据，覆盖demo数据。发现子组件mounted阶段打印的还是demo数据，而不是请求的数据，所以知道问题原因就是子组件渲染的时候，在父组件created请求后台数据返回之前就prop传递给了子组件，所以导致子组件获取的都不是从后台请求的数据。
3、刚开始子组件时在mounted里面调用画图方法drawline()，由于这时数据为空，所以报错。我就考虑到是不是不让子组件自身去mounte画图，而是让父组件异步请求到后台数据之后，赋值给prop之后，再通过ref去调用子组件的画图方法drawLine()，这样是不是就可以画图成功了？但是验证还是不行。在drawLine()里面去打印父组件传递的prop，发现还是最初的空或者demo数据。
所以考虑到父组件传递prop就是渲染时传递，而不是赋值时传递，所以总是传递的data()里面初始化的数据。所以通过父组件去调用子组件方法去画图也行不通。
4、考虑到父组件传递prop就是渲染时传递。
那么我就可以给子组件加个判断 v-if 条件，当父组件从后台异步取到数据后，并且赋值给prop后，让flag = true再去渲染子组件，那么此时传递给子组件的prop就是异步获取到数据之后的值，图形就正常展示出来了。
5、全部代码：
miniLine子组件
<template>
<div :id="myId" :style="{width:‘100%‘,height:‘200px‘}"></div>
</template>
<script type="ecmascript-6">
export default {
data(){
return {
series:[]
}
},
props:[‘myId‘,‘lineDime‘,‘lineSeries‘],
methods:{
drawLine(){
let myLine = this.$echarts.init(document.getElementById(this.myId));
let option = {
color:[‘#1CA6F1‘,‘#C1D534‘,‘#C6504D‘],
tooltip: {
trigger: ‘axis‘
},
legend: {
icon:‘stack‘
},
grid: {
left: ‘3%‘,
right: ‘3%‘,
bottom: ‘3%‘,
top:‘15%‘,
containLabel: true
},
xAxis: [{
type: ‘category‘,
axisTick: {
alignWithLabel: true,
show:false
},
axisLabel:{
show:true,
formatter: function (value, index) {
return value.split(‘ ‘)[1];
}
}
}],
yAxis: [{
type: ‘value‘,
axisTick: {
show: false
},
splitLine:{
show:true
}
}],
dataset:{
dimensions:this.lineDime,
source:this.lineSeries
},
series: this.series
};
myLine.setOption(option);
window.addEventListener("resize", () => { myLine.resize();});
}
},
mounted(){
let _obj = {
type:‘line‘
}
this.series.length = this.lineDime.length - 1
this.series.fill(_obj)
this.drawLine()
}
}
</script>
<style scoped lang="stylus" rel="stylesheet">
</style>
monitor父组件
<template>
<el-main>
<el-row class="dbInfo">
<el-col :span="6">
<div class="panel-body">
<img src="../../assets/images/postgreSQL.jpg" height="60">
<p>{{dbInfo.version}}</p>
</div>
</el-col>
<el-col :span="6">
<div class="panel-body">
<p>Rows fetched/returned</p>
<div class="content" :style="{color:‘#C1D534‘}">{{dbInfo.fetchper}}<span>%</span></div>
</div>
</el-col>
<el-col :span="6">
<div class="panel-body">
<p>Database capacity</p>
<div class="content" :style="{color:‘#1CA6F1‘}">{{parseInt(dbInfo.dbsize)}}<span>MB</span></div>
</div>
</el-col>
<el-col :span="6">
<div class="panel-body">
<p>Max connections in use</p>
<div class="content" :style="{color:‘#C6504D‘}">{{dbInfo.conper}}<span>%</span></div>
</div>
</el-col>
</el-row>
<div class="query">
<el-date-picker
v-model="datetimerange"
type="datetimerange"
range-separator="至"
start-placeholder="开始时间"
end-placeholder="结束时间"
size="mini">
</el-date-picker>
<i class="el-icon-refresh" @click="refresh"></i>
</div>
<el-row :gutter="20">
<el-col :span="12">
<moniLine v-if="flag" :my-id="ids[0]" :line-dime="dimensions[0]" :line-series="monitorData"></moniLine>
</el-col>
<el-col :span="12">
<moniLine v-if="flag" :my-id="ids[1]" :line-dime="dimensions[1]" :line-series="monitorData"></moniLine>
</el-col>
</el-row>
<el-row :gutter="20">
<el-col :span="8">
<moniLine v-if="flag" :my-id="ids[2]" :line-dime="dimensions[2]" :line-series="monitorData"></moniLine>
</el-col>
<el-col :span="8">
<moniLine v-if="flag" :my-id="ids[3]" :line-dime="dimensions[3]" :line-series="monitorData"></moniLine>
</el-col>
<el-col :span="8">
<moniLine v-if="flag" :my-id="ids[4]" :line-dime="dimensions[4]" :line-series="monitorData"></moniLine>
</el-col>
</el-row>
<el-tabs v-model="activeName" type="border-card">
<el-tab-pane label="Sessions" name="first">
<el-table :data="sessions" size="mini">
<el-table-column prop="pid" label="Pid" width="60" align="center"></el-table-column>
<el-table-column prop="datname" label="Database" width="80" align="center"></el-table-column>
<el-table-column prop="usename" label="User" width="80" align="center"></el-table-column>
<el-table-column prop="application_name" label="Application" align="center"></el-table-column>
<el-table-column prop="client_addr" label="Client" width="140" align="center"></el-table-column>
<el-table-column prop="backend_start" label="Backend start" width="150" align="center"></el-table-column>
<el-table-column prop="state" label="State" width="70" align="center"></el-table-column>
<el-table-column prop="wait_event" label="Wait Event" align="center"></el-table-column>
<el-table-column prop="blocking_pids" label="Blocking PIDs" width="90" align="center"></el-table-column>
</el-table>
</el-tab-pane>
<el-tab-pane label="Locks" name="second">
<el-table :data="locks" size="mini">
<el-table-column prop="pid" label="Pid" width="60"></el-table-column>
<el-table-column prop="datname" label="Database" width="70"></el-table-column>
<el-table-column prop="locktype" label="Lock type" width="70"></el-table-column>
<el-table-column prop="relation" label="Target relation"></el-table-column>
<el-table-column prop="page" label="Page" width="50"></el-table-column>
<el-table-column prop="tuple" label="Tuple" width="50"></el-table-column>
<el-table-column prop="virtualxid" label="vXID(target)"></el-table-column>
<el-table-column prop="objsubid" label="XID(target)"></el-table-column>
<el-table-column prop="classid" label="Class" width="50"></el-table-column>
<el-table-column prop="objid" label="ObjectID" width="65"></el-table-column>
<el-table-column prop="transactionid" label="vXID(owner)" width="90"></el-table-column>
<el-table-column prop="mode" label="Mode"></el-table-column>
<el-table-column prop="granted" label="Granted" width="65">
<template slot-scope="scope">{{scope.row.granted ? ‘是‘ :‘否‘}}</template>
</el-table-column>
</el-table>
</el-tab-pane>
<el-tab-pane label="Prepared Transactions" name="third">
<el-table :data="transactions" size="mini">
<el-table-column prop="gid" label="Name"></el-table-column>
<el-table-column prop="database" label="Database"></el-table-column>
<el-table-column prop="owner" label="Owner"></el-table-column>
<el-table-column prop="transaction" label="XID"></el-table-column>
<el-table-column prop="prepared" label="Prepared at"></el-table-column>
</el-table>
</el-tab-pane>
<el-tab-pane label="Configuration" name="fourth">
<el-table :data="configs" size="mini">
<el-table-column prop="name" label="Name"></el-table-column>
<el-table-column prop="category" label="Category"></el-table-column>
<el-table-column prop="setting" label="Setting"></el-table-column>
<el-table-column prop="unit" label="Unit" width="50"></el-table-column>
<el-table-column prop="short_desc" label="Description"></el-table-column>
</el-table>
</el-tab-pane>
</el-tabs>
</el-main>
</template>
<script type="ecmascript-6">
import moniLine from ‘./moniLine‘
import {getMonitorApi,getPgSessionsApi,getPgLocksApi,getPgPretransApi,getPgConfigsApi,getPgDbinfosApi} from ‘@/apis‘
export default {
data(){
return {
flag:false,
ids:[‘myLine1‘,‘myLine2‘,‘myLine3‘,‘myLine4‘,‘myLine5‘],
dimensions:[
[‘snap_time‘,‘active‘,‘idle‘,‘total‘],
[‘snap_time‘,‘commits‘,‘rollbacks‘,‘transactions‘],
[‘snap_time‘,‘inserts‘,‘updates‘,‘deletes‘],
[‘snap_time‘,‘fetched‘,‘returned‘],
[‘snap_time‘,‘reads‘,‘hits‘]
],
monitorData:[],
activeName:‘first‘,
sessions:[],
locks:[],
transactions:[],
configs:[],
dbInfo:{},
datetimerange:[]
}
},
components:{
moniLine
},
created(){
this.fetchData()
},
methods:{
fetchData(){
getMonitorApi().then(res => {
if(res.status === 200){
this.monitorData = res.data
this.flag = true
}
})
getPgSessionsApi().then(res => {
if(res.status === 200){
this.sessions = res.data
}
})
getPgLocksApi().then(res => {
if(res.status === 200){
this.locks = res.data
}
})
getPgPretransApi().then(res => {
if(res.status === 200){
this.transactions = res.data
}
})
getPgConfigsApi().then(res => {
if(res.status === 200){
this.configs = res.data
}
})
getPgDbinfosApi().then(res => {
if(res.status === 200){
this.dbInfo = res.data
}
})
},
refresh(){
this.fetchData()
}
}
}
</script>
<style scoped lang="stylus" rel="stylesheet">
@import ‘../../assets/css/index.styl‘
.el-row{
margin-bottom 20px
}
.query{
margin 10px
i{
font-weight 1000
color #A0A0A6
}
& i:hover{
color #1CA6F1
cursor pointer
}
}
.el-table{
font-size 10px
}
.el-tabs__nav .el-tabs__item{
font-size 12px
}
.dbInfo{
text-align center
p{
margin 0px
font-size 12px
}
.panel-body{
margin 10px 20px
min-height 82px
.content{
font-size 50px
font-weight 500
span{
font-size 30px
}
}
}
}
</style>
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