# useContent

Learn how to fetch content using composables.

This composable fetches the content of a [Slot](/explanation/slot), serving as the imperative equivalent of the [`<Slot>`](/reference/sdk/vue/api/components/slot-content) component.

## Signature

This composable has the following signature:

```ts
function useContent<T extends SlotId>(
    id: MaybeRefOrGetter<T>,
    options?: MaybeRefOrGetter<UseContentOptions>,
): UseContentResult<T>;
```

Where `UseContentResult<T>` is:

```ts
type UseContentResult<T> = {
    data: ShallowRef<SlotContent<T> | undefined>;
    metadata: ShallowRef<ContentMetadata | undefined>;
    isLoading: Ref<boolean>;
    error: Ref<Error | null>;
};
```

## Example

Here is an example of how to use this composable:

**JavaScript**

```vue
<script setup>
import {useContent} from '@croct/plug-vue';

const {data} = useContent('home-hero');
</script>

<template>
  <div v-if="data">
    <strong>{{ data.title }}</strong>
    <p>{{ data.subtitle }}</p>
    <a :href="data.button.link">{{ data.button.label }}</a>
  </div>
</template>
```

**TypeScript**

```vue
<script setup lang="ts">
import {useContent} from '@croct/plug-vue';

const {data} = useContent('home-hero');
</script>

<template>
  <div v-if="data">
    <strong>{{ data.title }}</strong>
    <p>{{ data.subtitle }}</p>
    <a :href="data.button.link">{{ data.button.label }}</a>
  </div>
</template>
```

## Parameters

- `id`: `string`

  The ID of the slot to fetch.

  You can specify the version of the slot by passing a versioned ID in the form `id@version`. For example, passing `home-hero@1` will fetch the content for the `home-hero` slot in version 1. Not specifying a version number is the same as passing `home-hero@latest`, which will load the content for the latest version.

  > **Best practice**
  >
  > Always specify a version to ensure the front end receives content with the expected structure despite future schema changes.
  >
  > For more information, see [Slot versioning](/explanation/slot#versioning).

- `options`: `object` (optional)

  The fetch options. Accepts a `MaybeRefOrGetter` for reactivity.

  - `initial`: `JSON` (optional)

    An initial value to render while loading the actual content.

    > **Auto-provided**
    >
    > If you are using the Croct CLI, you do not need to set an initial value unless you want to use a different one.

    This value is required for server-side rendering. For client-side rendering, not specifying this value will cause the `data` ref to be `undefined` and `isLoading` to be `true` until the content is fetched.

  - `fallback`: `JSON` (optional)

    A fallback value to use in case of an error.

    > **Auto-provided**
    >
    > If you are using the Croct CLI, you do not need to set a fallback unless you want to use a different one.

    If not specified, the `error` ref will contain the error and `data` will remain `undefined`.

  - `expiration`: `number` (optional) (default: 60000)

    The cache expiration time in milliseconds, extended on every render.

    If negative, the cache never expires. By default, the cache expires after 60 seconds.

    The SDK caches the result to prevent network requests on concurrent renders and re-renders.

  - `cacheKey`: `string` (optional)

    A unique key to identify the cache entry.

    By default, the cache key is derived from the slot ID, locale, and attributes. You can specify a custom cache key to force re-fetching even if the other parameters are the same.

  - `staleWhileLoading`: `boolean` (optional) (default: false)

    Whether to use the previous content while re-fetching the content.

    By default, the composable sets `data` to `undefined` and `isLoading` to `true` while loading new content.

    If this option is enabled, the behavior changes as follows:

    - On the first render, it either returns the initial content or sets `isLoading` to `true` while fetching.
    - If the cache key or any other property that affects the content changes, it returns the previous content while fetching the new content.
    - When the new content is available, it updates `data` with the new content.

  - `preferredLocale`: `string` (optional) (default: default locale)

    The locale code to fetch the content.

    The code consists of a two-part string that specifies the language and, optionally, the country. For example, `en` represents English, `en-us` stands for English (United States), and `pt-br` for Portuguese (Brazil). It is case-insensitive and supports both hyphens and underscores as separators to accommodate the different conventions used by browsers, libraries, and other systems.

    If no content is available in the preferred locale, the default locale content is returned instead.

  - `timeout`: `number` (optional)

    The maximum fetch time in milliseconds.

    Once reached, the SDK will abort the request and reject the promise with a timeout error.

  - `attributes`: `object` (optional)

    The map of attributes to inject in the evaluation context.

    The attributes can be referenced in audience conditions using the [`context`](/reference/cql/context#evaluation) variable. For example, suppose you pass the following attributes:

    ```json
    {cities: ["New York", "San Francisco"]}
    ```

    You can then reference them in queries like:

    ```cql
    context's cities include location's cityName
    ```

    For more information, see [Context variables](../../content-rendering#context-variables).

    The following restrictions apply to the attributes:

    - Up to 30 entries and 5 levels deep
    - Keys can be either numbers or non-empty strings with a maximum length of 50 characters
    - Values can be null, numbers, booleans, strings (up to 50 characters), or nested maps
    - Nested maps follow the same constraints for keys and values

## Return

The return is a reactive object with the following properties:

- `data`: `ShallowRef<SlotContent | undefined>` (see [SlotContent](../types/slot-content))

  A shallow ref containing the slot content, or `undefined` while loading.

- `metadata`: `ShallowRef<ContentMetadata | undefined>`

  A shallow ref containing the content metadata, or `undefined` while loading or if not available.

- `isLoading`: `Ref<boolean>`

  A ref indicating whether the content is currently being fetched.

- `error`: `Ref<Error | null>`

  A ref containing the error if the fetch failed, or `null` otherwise.