I’m using Vue.js and Chart.js to draw some charts.
Each time I call the function generateChart(), the chart is not updated automatically. When I check the data in Vue Devtools, they are correct but the chart does not reflect the data. However, the chart does update when I resize the window.
- What is wrong with what I’m doing?
- How do I update the chart each time I call
generateChart()?
I feel this is going to be something related with object and array change detection caveats, but I’m not sure what to do.
https://codepen.io/anon/pen/bWRVKB?editors=1010
<template>
<el-dialog title="Chart" v-model="showGeneratedChart">
<line-chart :chartData="dataChart"></line-chart>
</el-dialog>
</template>
<script>
export default {
data() {
const self = this;
return {
dataChart: {
labels: [],
datasets: [
{
label: "label",
backgroundColor: "#FC2525",
data: [0, 1, 2, 3, 4],
},
],
},
};
},
methods: {
generateChart() {
this.dataChart["labels"] = [];
this.dataChart["datasets"] = [];
// ... compute datasets and formattedLabels
this.dataChart["labels"] = formattedLabels;
this.dataChart["datasets"] = datasets;
},
},
};
</script>
LineChart.js
import { Line, mixins } from 'vue-chartjs'
export default Line.extend({
mixins: [mixins.reactiveProp],
props: ["options"],
mounted () {
this.renderChart(this.chartData, this.options)
}
})
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Answer
Use a computed property for the chart data. And instead of calling this.renderChart on watch wrap it in a method and reuse that method on mounted and in watch.
Vue.component("line-chart", {
extends: VueChartJs.Line,
props: ["data", "options"],
mounted() {
this.renderLineChart();
},
computed: {
chartData: function() {
return this.data;
}
},
methods: {
renderLineChart: function() {
this.renderChart(
{
labels: [
"January",
"February",
"March",
"April",
"May",
"June",
"July"
],
datasets: [
{
label: "Data One",
backgroundColor: "#f87979",
data: this.chartData
}
]
},
{ responsive: true, maintainAspectRatio: false }
);
}
},
watch: {
data: function() {
this._chart.destroy();
//this.renderChart(this.data, this.options);
this.renderLineChart();
}
}
});
var vm = new Vue({
el: ".app",
data: {
message: "Hello World",
dataChart: [10, 39, 10, 40, 39, 0, 0],
test: [4, 4, 4, 4, 4, 4]
},
methods: {
changeData: function() {
this.dataChart = [6, 6, 3, 5, 5, 6];
}
}
});<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width">
<title>Vue.jS Chart</title>
</head>
<body>
<div class="app">
{{ dataChart }}
<button v-on:click="changeData">Change data</button>
<line-chart :data="dataChart" :options="{responsive: true, maintainAspectRatio: false}"></line-chart>
</div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.2.6/vue.min.js"></script>
<script src="https://unpkg.com/vue-chartjs@2.5.7-rc3/dist/vue-chartjs.full.min.js"></script>
</body>
</html>You could also make the options a computed property, and if option not going to change much you can setup default props. https://v2.vuejs.org/v2/guide/components.html#Prop-Validation
Here is a working codepen https://codepen.io/azs06/pen/KmqyaN?editors=1010