Nuxt3: [useAsyncData] Component is already mounted, why?

When working with Nuxt and needing to handle asynchronous data fetching, it’s important to understand the appropriate contexts and methods to use. Here’s a breakdown of the best practices and approaches:

Composables in Nuxt

useAsyncData and useAsyncQuery

• Usage: These composables are designed to be used at the top level of a setup function.
• Limitation: They cannot be called within event handlers. This is due to their composable nature, which requires them to be executed during the component’s setup phase, ensuring that the data fetching logic is integrated with the component’s lifecycle.

Making Requests in Event Handlers

• Recommended Approach: Use $fetch when making requests within event handlers. This method is suitable for actions triggered by user interactions, such as button clicks or form submissions.
• Why: $fetch can be called at any time, providing flexibility for event-driven data fetching without the lifecycle constraints of composables.

Nuxt Apollo

• Usage: To integrate Apollo Client for GraphQL queries, you should use the useApollo composable.
• Procedure:
  1. Setup Function: Call useApollo within your component’s setup function to obtain an Apollo client instance.
  2. Event Handlers: Use the obtained Apollo client to perform queries or mutations within your event handlers.

Example Implementation

Here’s a practical example to illustrate these concepts:

Fetching Data with $fetch in an Event Handler

<template>
  <div>
    <button @click="fetchData">Fetch Data</button>
    <div v-if="data">{{ data }}</div>
  </div>
</template>

<script setup>
import { ref } from 'vue';

const data = ref(null);

const fetchData = async () => {
  try {
    data.value = await $fetch('/api/data-endpoint');
  } catch (error) {
    console.error('Error fetching data:', error);
  }
};
</script>

Using Apollo Client in an Event Handler

<template>
  <div>
    <button @click="fetchGraphQLData">Fetch GraphQL Data</button>
    <div v-if="data">{{ data }}</div>
  </div>
</template>

<script setup>
import { ref } from 'vue';
import { useApollo } from '@nuxtjs/apollo-composable';

const { apolloClient } = useApollo();
const data = ref(null);

const fetchGraphQLData = async () => {
  try {
    const result = await apolloClient.query({
      query: gql`
        query {
          myQuery {
            field1
            field2
          }
        }
      `
    });
    data.value = result.data.myQuery;
  } catch (error) {
    console.error('Error fetching GraphQL data:', error);
  }
};
</script>

Further Reading

To deepen your understanding of data fetching in Nuxt, refer to the official documentation here.

Following these guidelines, you can effectively manage asynchronous data fetching in Nuxt, ensuring your application remains responsive and maintainable.