What is causing the chartjs graph to fail to load in Vue.js?

Here's my Chartjs component, where I'm attempting to pass two arrays from the backend using Vue.js. Despite successfully retrieving the arrays within Vue, nothing is displaying on the chart. As a newcomer to Vue, I appreciate your patience.

Chartjs.vue

<template>
  <div class="main-content">
    // other code here ...
  </div>
</template>

<script type="text/babel">
// import statements and component definitions here ...

export default {
  components: {
    // referenced chart components here ...
  },
  methods: {
    async fetchBarChartData ({ anio, sort }) {
      // fetching data from API endpoint here ...
    }
  },
  mounted() {
      this.fetchBarChartData({anio:2018});
  },
  data () {
    return {
      // hardcoded chart labels and initial values setup here ...
    }
  }
}
</script>

BarLineChart.vue

<template>
  <div class="graph-container">
    <canvas id="graph" ref="graph"/>
  </div>
</template>

<script>
// component logic for rendering the Bar Line chart here ...
</script>

<style scoped>
.graph-container {
  height: 300px;
}
</style>

In troubleshooting, I discovered that adding ".data" to the values array caused one component to break while others continued displaying charts below it.

If anyone has encountered similar issues or has experience with this, I would greatly appreciate any guidance. The dashboard template I'm using can be found at laraspace.in.

EDIT: For easier assistance, I've created a codesandbox for this project:

https://codesandbox.io/embed/vue-template-x4z7b

EDIT 2: While I was able to get it working with local values in the sandbox environment, I'm facing difficulties when making API calls locally.

Answer №1

I must confess, the documentation for fetching async data in vuejs and integrating it into your application is lacking. It would be beneficial if they provided more guidance on best practices along with additional examples.

The Issue: A component relying on async data

When making an asynchronous API call, this.values remains an empty array (this.values.data doesn't exist until the API call returns). As a result, when the child component that creates a chart using this empty values array is created before the data arrives, a blank chart is displayed. To remedy this situation, you need to ensure that the data is loaded before creating the child component (and consequently the chart). But how can you achieve this?

The Solution: Conditional component rendering

  1. Retrieve data in the created hook instead of the mounted hook. Why? Requesting data earlier enhances performance, refer to: https://v2.vuejs.org/v2/guide/instance.html
  2. Upon receiving the data response, store it in your Vue component. Why? You require that data, see: https://v2.vuejs.org/v2/cookbook/using-axios-to-consume-apis.html#ad
  3. After saving the data, indicate to your HTML that the data is ready by using a variable this.loaded = true and utilize v-if="loaded" on any child components dependent on that data, explore: https://v2.vuejs.org/v2/guide/conditional.html

For a demonstration, here's a functional code sandbox featuring a mock API call replicating your modifications: https://codesandbox.io/s/vue-template-4b3lm

All alterations were done within the Chartjs.vue file.

Additional Mistakes Noticed:

  • Declaring variables within the component section
  • Excessive setting of this.values in multiple places. Simply define it once in data and adjust it as necessary later on.

Alternative Approach for Resolving this Issue:

  • Utilize a watcher in the child components instead of v-if: to refresh the chart inside the component (without delaying the entire component) when the data arrives (every time the props change).
  • Incorporate Vuex

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