---
url: /guide/advanced/data-fetching.md
---
# Data Fetching

Sometimes you need to fetch data from the server when a route is activated. For example, before rendering a user profile, you need to fetch the user's data from the server. We can achieve this in two different ways:

* **Fetching After Navigation**: perform the navigation first, and fetch data in the incoming component's lifecycle hook. Display a loading state while data is being fetched.

* **Fetching Before Navigation**: Fetch data before navigation in the route enter guard, and perform the navigation after data has been fetched.

Technically, both are valid choices - it ultimately depends on the user experience you are aiming for.

## Fetching After Navigation

When using this approach, we navigate and render the incoming component immediately, and fetch data in the component itself. It gives us the opportunity to display a loading state while the data is being fetched over the network, and we can also handle loading differently for each view.

Let's assume we have a `Post` component that needs to fetch the data for a post based on `route.params.id`:

::: code-group

```vue [Composition API]
<template>
  <div class="post">
    <div v-if="loading" class="loading">Loading...</div>

    <div v-if="error" class="error">{{ error }}</div>

    <div v-if="post" class="content">
      <h2>{{ post.title }}</h2>
      <p>{{ post.body }}</p>
    </div>
  </div>
</template>

<script setup>
import { ref, watch } from 'vue'
import { useRoute } from 'vue-router'
import { getPost } from './api.js'

const route = useRoute()

const loading = ref(false)
const post = ref(null)
const error = ref(null)

// watch the params of the route to fetch the data again
watch(() => route.params.id, fetchData, { immediate: true })

async function fetchData(id) {
  error.value = post.value = null
  loading.value = true

  try {
    // replace `getPost` with your data fetching util / API wrapper
    post.value = await getPost(id)
  } catch (err) {
    error.value = err.toString()
  } finally {
    loading.value = false
  }
}
</script>
```

```vue [Options API]
<template>
  <div class="post">
    <div v-if="loading" class="loading">Loading...</div>

    <div v-if="error" class="error">{{ error }}</div>

    <div v-if="post" class="content">
      <h2>{{ post.title }}</h2>
      <p>{{ post.body }}</p>
    </div>
  </div>
</template>

<script>
import { getPost } from './api.js'

export default {
  data() {
    return {
      loading: false,
      post: null,
      error: null,
    }
  },
  created() {
    // watch the params of the route to fetch the data again
    this.$watch(
      () => this.$route.params.id,
      this.fetchData,
      // fetch the data when the view is created and the data is
      // already being observed
      { immediate: true }
    )
  },
  methods: {
    async fetchData(id) {
      this.error = this.post = null
      this.loading = true

      try {
        // replace `getPost` with your data fetching util / API wrapper
        this.post = await getPost(id)
      } catch (err) {
        this.error = err.toString()
      } finally {
        this.loading = false
      }
    },
  },
}
</script>
```

:::

## Fetching Before Navigation

With this approach we fetch the data before actually navigating to the new route. We can perform the data fetching in the `beforeRouteEnter` guard in the incoming component, and only call `next` when the fetch is complete. The callback passed to `next` will be called **after the component is mounted**:

```js
export default {
  data() {
    return {
      post: null,
      error: null,
    }
  },
  async beforeRouteEnter(to, from, next) {
    try {
      const post = await getPost(to.params.id)
      // `setPost` is a method defined below
      next(vm => vm.setPost(post))
    } catch (err) {
      // `setError` is a method defined below
      next(vm => vm.setError(err))
    }
  },
  // when route changes and this component is already rendered,
  // the logic will be slightly different.
  beforeRouteUpdate(to, from) {
    this.post = null
    getPost(to.params.id).then(this.setPost).catch(this.setError)
  },
  methods: {
    setPost(post) {
      this.post = post
    },
    setError(err) {
      this.error = err.toString()
    },
  },
}
```

The user will stay on the previous view while the resource is being fetched for the incoming view. It is therefore recommended to display a progress bar or some kind of indicator while the data is being fetched. If the data fetch fails, it's also necessary to display some kind of global warning message.