npm package: @steerapi/swr-firestore
Description: SWR React hooks for Firestore, that you can actually use in production, on every screen.
Author: Fernando Rojo
Latest version: 0.17.1

# SWR + Firestore

```js
const { data } = useDocument('users/fernando')
```

**It's that easy.**

🔥 This library provides the hooks you need for querying Firestore, that you can actually use in production, on every screen.

⚡️ It aims to be **the fastest way to use Firestore in a React app,** both from a developer experience and app performance perspective.

🍕 This library is built on top [useSWR](https://swr.now.sh), meaning you get all of its awesome benefits out-of-the-box.

You can now fetch, add, and mutate Firestore data with zero boilerplate.

## Features

- Shared state / cache between collection and document queries [(instead of Redux??)](#shared-global-state-between-documents-and-collections)
- Works with both **React** and **React Native**.
- Offline mode with Expo [(without detaching!)](https://github.com/nandorojo/expo-firestore-offline-persistence/blob/master/README.md#usage-with-nandorojoswr-firestore)
- Blazing fast
- Query collection groups (**new** in `0.14.x`!)
- `set`, `update`, and `add` update your global cache, instantly
- TypeScript-ready [(see docs)](#typescript-support)
- Realtime subscriptions [(example)](#simple-examples)
- Prevent memory leaks from Firestore subscriptions
- No more parsing `document.data()` from Firestore requests
- Server-side rendering (SSR or SSG) with Next.js [(example)](https://github.com/nandorojo/swr-firestore/issues/17)
- Automatic date parsing (no more `.toDate()`)
- Firebase v8 support (see [#59](https://github.com/nandorojo/swr-firestore/issues/59#issuecomment-719950071))

...along with the features touted by Vercel's incredible [SWR](https://github.com/zeit/swr#introduction) library:

_"With SWR, components will get a stream of data updates constantly and automatically. Thus, the **UI will be always fast and reactive**."_

- Transport and protocol agnostic data fetching
- Fast page navigation
- Revalidation on focus
- Interval polling
- Request deduplication
- Local mutation
- Pagination
- TypeScript ready
- SSR support
- Suspense mode
- Minimal API

## ⭐️

If you like this library, give it star and let me know on [Twitter](https://twitter.com/fernandotherojo)!

## Installation

```sh
yarn add @nandorojo/swr-firestore

# or
npm install @nandorojo/swr-firestore
```

Install firebase:

```sh
# if you're using expo:
expo install firebase

# if you aren't using expo:
yarn add firebase
# or
npm i firebase
```

## Set up

In the root of your app, **create an instance of Fuego** and pass it to the **FuegoProvider**.

If you're using Firebase v8, see [this solution](https://github.com/nandorojo/swr-firestore/issues/59#issuecomment-719950071) for creating your instance of `Fuego`.

If you're using `next.js`, this goes in your `pages/_app.js` file.

`App.js`

```jsx
import React from 'react'
import 'firebase/firestore'
import 'firebase/auth'
import { Fuego, FuegoProvider } from '@nandorojo/swr-firestore'

const firebaseConfig = {
  // put yours here
}

const fuego = new Fuego(firebaseConfig)

export default function App() {
  return (
    <FuegoProvider fuego={fuego}>
      <YourAppHere />
    </FuegoProvider>
  )
}
```

Make sure to create your `Fuego` instance outside of the component. The only argument `Fuego` takes is your firebase `config` variable.

Under the hood, this step initializes firebase for you. No need to call `firebase.initializeApp`.

## Basic Usage

_Assuming you've already completed the setup..._

### Subscribe to a document

```js
import React from 'react'
import { useDocument } from '@nandorojo/swr-firestore'
import { Text } from 'react-native'

export default function User() {
  const user = { id: 'Fernando' }
  const { data, update, error } = useDocument(`users/${user.id}`, {
    listen: true,
  })

  if (error) return <Text>Error!</Text>
  if (!data) return <Text>Loading...</Text>

  return <Text>Name: {data.name}</Text>
}
```

### Get a collection

```js
import React from 'react'
import { useCollection } from '@nandorojo/swr-firestore'
import { Text } from 'react-native'

export default function UserList() {
  const { data, update, error } = useCollection(`users`)

  if (error) return <Text>Error!</Text>
  if (!data) return <Text>Loading...</Text>

  return data.map(user => <Text key={user.id}>{user.name}</Text>)
}
```

`useDocument` accepts a document `path` as its first argument here. `useCollection` works similarly.

## Simple examples

### Query a users collection:

```typescript
const { data } = useCollection('users')
```

### Subscribe for real-time updates:

```typescript
const { data } = useDocument(`users/${user.id}`, { listen: true })
```

### Make a complex collection query:

```typescript
const { data } = useCollection('users', {
  where: ['name', '==', 'fernando'],
  limit: 10,
  orderBy: ['age', 'desc'],
  listen: true,
})
```

### Pass options from SWR to your document query:

```typescript
// pass SWR options
const { data } = useDocument('albums/nothing-was-the-same', {
  shouldRetryOnError: false,
  onSuccess: console.log,
  loadingTimeout: 2000,
})
```

### Pass options from SWR to your collection query:

```typescript
// pass SWR options
const { data } = useCollection(
  'albums',
  {
    listen: true,
    // you can pass multiple where conditions if you want
    where: [
      ['artist', '==', 'Drake'],
      ['year', '==', '2020'],
    ],
  },
  {
    shouldRetryOnError: false,
    onSuccess: console.log,
    loadingTimeout: 2000,
  }
)
```

### Add data to your collection:

```typescript
const { data, add } = useCollection('albums', {
  where: ['artist', '==', 'Drake'],
})

const onPress = async () => {
  // calling this will automatically update your global cache & Firestore
  const documentId = await add({
    title: 'Dark Lane Demo Tapes',
    artist: 'Drake',
    year: '2020',
  })
}
```

### Set document data:

```typescript
const { data, set, update } = useDocument('albums/dark-lane-demo-tapes')

const onReleaseAlbum = () => {
  // calling this will automatically update your global cache & Firestore
  set(
    {
      released: true,
    },
    { merge: true }
  )

  // or you could call this:
  update({
    released: true,
  })
}
```

### Use dynamic fields in a request:

If you pass `null` as the collection or document key, the request won't send.

Once the key is set to a string, the request will send.

**Get list of users who have you in their friends list**

```typescript
import { useDoormanUser } from 'react-doorman'

const { uid } = useDoormanUser()
const { data } = useCollection(uid ? 'users' : null, {
  where: ['friends', 'array-contains', uid],
})
```

**Get your favorite song**

```typescript
const me = { id: 'fernando' }

const { data: user } = useDocument<{ favoriteSong: string }>(`users/${me.id}`)

// only send the request once the user.favoriteSong exists!
const { data: song } = useDocument(
  user?.favoriteSong ? `songs/${user.favoriteSong}` : null
)
```

### Parse date fields in your documents

Magically turn any Firestore timestamps into JS date objects! No more `.toDate()`.

Imagine your `user` document schema looks like this:

```typescript
type User = {
  name: string
  lastUpdated: {
    date: Date
  }
  createdAt: Date
}
```

In order to turn `createdAt` and `lastUpdated.date` into JS objects, just use the `parseDates` field:

**In a document query**

```typescript
const { data } = useDocument<User>('user/fernando', {
  parseDates: ['createdAt', 'lastUpdated.date'],
})

let createdAt: Date
if (data) {
  // ✅ all good! it's a JS Date now.
  createdAt = data.createdAt
}
```

`data.createdAt` and `data.lastUpdated.date` are both JS dates now!

**In a collection query**

```typescript
const { data } = useCollection<User>('user', {
  parseDates: ['createdAt', 'lastUpdated.date'],
})

if (data) {
  data.forEach(document => {
    document.createdAt // JS date!
  })
}
```

For more explanation on the dates, see [issue #4](https://github.com/nandorojo/swr-firestore/issues/4).

### Access a document's Firestore snapshot

If you set `ignoreFirestoreDocumentSnapshotField` to `false`, you can access the `__snapshot` field.

```js
const { data } = useDocument('users/fernando', {
  ignoreFirestoreDocumentSnapshotField: false, // default: true
})

if (data) {
  const id = data?.__snapshot.id
}
```

You can do the same for `useCollection` and `useCollectionGroup`. The snapshot will be on each item in the `data` array.

This comes in handy when you are working with forms for data edits:

**With Formik**
```js
const { data, set } = useDocument('users/fernando', {
  ignoreFirestoreDocumentSnapshotField: false,
})

if (!data) return <Loading />

<Formik
  initialValues={data.__snapshot.data()}
  ...
/>
```

**With state and hooks**
```js
const { data, set } = useDocument('users/fernando', {
  ignoreFirestoreDocumentSnapshotField: false,
})

const [values, setValues] = useState(null);

useEffect(() => {
  if (data) {
    setValues(data.__snapshot.data());
  }
}, [data]);
```

### Paginate a collection:

Video [here](https://imgur.com/a/o9AlI4N).

```typescript
import React from 'react'
import { fuego, useCollection } from '@nandorojo/swr-firestore'

const collection = 'dump'
const limit = 1
const orderBy = 'text'

export default function Paginate() {
  const { data, mutate } = useCollection<{ text: string }>(
    collection,
    {
      limit,
      orderBy,
      // 🚨 this is required to get access to the snapshot!
      ignoreFirestoreDocumentSnapshotField: false,
    },
    {
      // this lets us update the local cache + paginate without interruptions
      revalidateOnFocus: false,
      refreshWhenHidden: false,
      refreshWhenOffline: false,
      refreshInterval: 0,
    }
  )

  const paginate = async () => {
    if (!data?.length) return

    const ref = fuego.db.collection(collection)

    // get the snapshot of last document we have right now in our query
    const startAfterDocument = data[data.length - 1].__snapshot

    // get more documents, after the most recent one we have
    const moreDocs = await ref
      .orderBy(orderBy)
      .startAfter(startAfterDocument)
      .limit(limit)
      .get()
      .then(d => {
        const docs = []
        d.docs.forEach(doc => docs.push({ ...doc.data(), id: doc.id, __snapshot: doc }))
        return docs
      })

    // mutate our local cache, adding the docs we just added
    // set revalidate to false to prevent SWR from revalidating on its own
    mutate(state => [...state, ...moreDocs], false)
  }

  return data ? (
    <div>
      {data.map(({ id, text }) => (
        <div key={id}>{text}</div>
      ))}
      <button onClick={paginate}>paginate</button>
    </div>
  ) : (
    <div>Loading...</div>
  )
}
```

## Query Documents

You'll rely on `useDocument` to query documents.

```js
import React from 'react'
import { useDocument } from '@nandorojo/swr-firestore'

const user = { id: 'Fernando' }
export default () => {
  const { data, error } = useDocument(`users/${user.id}`)
}
```

If you want to set up a listener (or, in Firestore-speak, `onSnapshot`) just set `listen` to `true`.

```js
const { data, error } = useDocument(`users/${user.id}`, { listen: true })
```

# API

## Imports

```typescript
import {
  useDocument,
  useCollection,
  useCollectionGroup, // 👋 new!
  revalidateDocument,
  revalidateCollection,
  // these all update BOTH Firestore & the local cache ⚡️
  set, // set a firestore document
  update, // update a firestore document
  fuego, // get the firebase instance used by this lib
  getCollection, // prefetch a collection, without being hooked into SWR or React
  getDocument, // prefetch a document, without being hooked into SWR or React
} from '@nandorojo/swr-firestore'
```

## `useDocument(path, options)`

```js
const {
  data,
  set,
  update,
  deleteDocument,
  error,
  isValidating,
  mutate,
  unsubscribe
} = useDocument(path, options)
```

### Arguments

- **`path` required** The unique document path for your Firestore document.
  - `string` | `null`. If `null`, the request will not be sent. This is useful if you want to get a user document, but the user ID hasn't loaded yet, for instance.
  - This follows the same pattern as the `key` argument in `useSWR`. See the [SWR docs](https://github.com/zeit/swr#conditional-fetching) for more. Functions are not currently supported for this argument.
- `options` _(optional)_ A dictionary with added options for the query. Takes the folowing values:
  - `listen = false`: If `true`, sets up a listener for this document that updates whenever it changes.
  - You can also pass any of the [options available from `useSWR`](https://github.com/zeit/swr#options).
  - `ignoreFirestoreDocumentSnapshotField = true`. See elaboration below.
  - `parseDates`: An array of string keys that correspond to dates in your document. [Example](#parse-date-fields-in-your-documents).

##### `ignoreFirestoreDocumentSnapshotField`

If `true`, docs returned in `data` will not include the firestore `__snapshot` field. If `false`, it will include a `__snapshot` field. This lets you access the document snapshot, but makes the document not JSON serializable.

By default, it ignores the `__snapshot` field. This makes it easier for newcomers to use `JSON.stringify` without weird errors. You must explicitly set it to `false` to use it.

```js
// include the firestore document snapshots
const { data } = useDocument('users/fernando', {
  ignoreFirestoreDocumentSnapshotField: false,
})

if (data) {
  const path = data.__snapshot.ref.path
}
```

The `__snapshot` field is the exact snapshot returned by Firestore.

See Firestore's [snapshot docs](https://firebase.google.com/docs/reference/js/firebase.firestore.QuerySnapshot) for more.

### Return values

Returns a dictionary with the following values:

- `set(data, SetOptions?)`: Extends the `firestore` document `set` function.
  - You can call this when you want to edit your document.
  - It also updates the local cache using SWR's `mutate`. This will prove highly convenient over the regular Firestore `set` function.
  - The second argument is the same as the second argument for [Firestore `set`](https://firebase.google.com/docs/firestore/manage-data/add-data#set_a_document).
- `update(data)`: Extends the Firestore document [`update` function](https://firebase.google.com/docs/firestore/manage-data/add-data#update-data).
  - It also updates the local cache using SWR's `mutate`. This will prove highly convenient over the regular `set` function.
- `deleteDocument()`: Extends the Firestore document [`delete` function](https://firebase.google.com/docs/firestore/manage-data/delete-data).
  - It also updates the local cache using SWR's `mutate` by deleting your document from this query and all collection queries that have fetched this document. This will prove highly convenient over the regular `delete` function from Firestore.
- `unsubscribe()` A function that, when called, unsubscribes the Firestore listener.
  - The function can be null, so make sure to check that it exists before calling it.
  - **Note**: This is not necessary to use. `useDocument` already unmounts the listener for you. This is only intended if you want to unsubscribe on your own.

The dictionary also includes the following [from `useSWR`](https://github.com/zeit/swr#return-values):

- `data`: data for the given key resolved by fetcher (or undefined if not loaded)
- `error`: error thrown by fetcher (or undefined)
- `isValidating`: if there's a request or revalidation loading
- `mutate(data?, shouldRevalidate?)`: function to mutate the cached data

## `useCollection(path, query, options)`

```js
const { data, add, error, isValidating, mutate, unsubscribe } = useCollection(
  path,
  query,
  options
)
```

### Arguments

- **`path`** required string, path to collection.
- `query` optional dictionary with Firestore query details
- `options` SWR options [(see SWR docs)](https://github.com/zeit/swr#options)

#### `path`

**`path` required** The unique document path for your Firestore document.

- `string` | `null`. If `null`, the request will not be sent. This is useful if you want to get a user document, but the user ID hasn't loaded yet, for instance.
- This follows the same pattern as the `key` argument in `useSWR`. See the [SWR docs](https://github.com/zeit/swr#conditional-fetching) for more. Functions are not currently supported for this argument.

#### `query`

_(optional)_ Dictionary that accepts any of the following optional values:

- `listen = false`: if true, will set up a real-time listener that automatically updates.
- `limit`: number that limits the number of documents
- [`where`](#where): filter documents by certain conditions based on their fields
- [`orderBy`](#orderBy): sort documents by their fields
- `startAt`: number to start at
- `endAt`: number to end at
- `startAfter`: number to start after
- `endBefore`: number to end before
- `ignoreFirestoreDocumentSnapshotField = true`: If `true`, docs returned in `data` will not include the firestore `__snapshot` field. If `false`, it will include a `__snapshot` field. This lets you access the document snapshot, but makes the document not JSON serializable.

##### `where`

Can be an array, or an array of arrays.

Each array follows this outline: `['key', 'comparison-operator', 'value']`. This is pulled directly from Firestore's [where pattern](https://firebase.google.com/docs/firestore/query-data/queries#query_operators).

```js
// get all users whose names are Fernando
useCollection('users', {
  where: ['name', '==', 'Fernando'],
})

// get all users whose names are Fernando & who are hungry
useCollection('users', {
  where: [
    ['name', '==', 'Fernando'],
    ['isHungry', '==', true],
  ],
})

// get all users whose friends array contains Fernando
useCollection('users', {
  where: ['friends', 'array-contains', 'Fernando'],
})
```

##### `orderBy`

Can be a string, array, or an array of arrays.

Each array follows this outline: `['key', 'desc' | 'asc']`. This is pulled directly from Firestore's [orderBy pattern](https://firebase.google.com/docs/firestore/query-data/order-limit-data).

```js
// get users, ordered by name
useCollection('users', {
  orderBy: 'name',
})

// get users, ordered by name in descending order
useCollection('users', {
  orderBy: ['name', 'desc'],
})

// get users, ordered by name in descending order & hunger in ascending order
useCollection('users', {
  orderBy: [
    ['name', 'desc'], //
    ['isHungry', 'asc'],
  ],
})
```

##### `ignoreFirestoreDocumentSnapshotField`

If `true`, docs returned in `data` will not include the firestore `__snapshot` field. If `false`, it will include a `__snapshot` field. This lets you access the document snapshot, but makes the document not JSON serializable.

By default, it ignores the `__snapshot` field. This makes it easier for newcomers to use `JSON.stringify` without weird errors. You must explicitly set it to `false` to use it.

```js
// include the firestore document snapshots
const { data } = useCollection('users', {
  ignoreFirestoreDocumentSnapshotField: false,
})

if (data) {
  data.forEach(document => {
    const path = document?.__snapshot.ref.path
  })
}
```

The `__snapshot` field is the exact snapshot returned by Firestore.

See Firestore's [snapshot docs](https://firebase.google.com/docs/reference/js/firebase.firestore.QuerySnapshot) for more.

#### `options`

_(optional)_ A dictionary with added options for the request. See the [options available from SWR](https://github.com/zeit/swr#options).

### Return values

Returns a dictionary with the following values:

- `add(data)`: Extends the Firestore document [`add` function](https://firebase.google.com/docs/firestore/manage-data/add-data). Returns the added document ID(s).
  - It also updates the local cache using SWR's `mutate`. This will prove highly convenient over the regular `add` function provided by Firestore.

The returned dictionary also includes the following [from `useSWR`](https://github.com/zeit/swr#return-values):

- `data`: data for the given key resolved by fetcher (or undefined if not loaded)
- `error`: error thrown by fetcher (or undefined)
- `isValidating`: if there's a request or revalidation loading
- `mutate(data?, shouldRevalidate?)`: function to mutate the cached data
- `unsubscribe()` A function that, when called, unsubscribes the Firestore listener.
  - The function can be null, so make sure to check that it exists before calling it.
  - **Note**: This is not necessary to use. `useCollection` already unmounts the listener for you. This is only intended if you want to unsubscribe on your own.

## `useCollectionGroup(path, query, options)`

Follows an identical API as `useCollection`, except that it leverages Firestore's collection group query for merging subcollections with the same name.

To see how to use it, follow the instructions from [`useCollection`](#useCollection).

See the Firestore [docs on collecttion groups](https://firebase.google.com/docs/firestore/query-data/queries) to learn more.

## `set(path, data, SetOptions?)`

Extends the `firestore` document `set` function.

- You can call this when you want to edit your document.
- It also updates the local cache using SWR's `mutate`. This will prove highly convenient over the regular Firestore `set` function.
- The second argument is the same as the second argument for [Firestore `set`](https://firebase.google.com/docs/firestore/manage-data/add-data#set_a_document).

This is useful if you want to `set` a document in a component that isn't connected to the `useDocument` hook.

## `update(path, data)`:

Extends the Firestore document [`update` function](https://firebase.google.com/docs/firestore/manage-data/add-data#update-data).

- It also updates the local cache using SWR's `mutate`. This will prove highly convenient over the regular `set` function.

This is useful if you want to `update` a document in a component that isn't connected to the `useDocument` hook.

<!--
## `add(path, data)`:

Extends the Firestore document [`add` function](https://firebase.google.com/docs/firestore/manage-data/add-data).

- It also updates the local cache using SWR's `mutate`. This will prove highly convenient over the regular `add` function.
- Use this **instead** of `firebase.firestore().collection('users').add(data)`
-->

## `deleteDocument(path, ignoreLocalMutations = false)`

Extends the Firestore document [`delete` function](https://firebase.google.com/docs/firestore/manage-data/delete-data).

- It also updates the local cache using SWR's `mutate` by deleting your document from this query and all collection queries that have fetched this document. This will prove highly convenient over the regular `delete` function from Firestore.
- Second argument is a boolean that defaults to false. If `true`, it will not update the local cache, and instead only send delete to Firestore.

## `revalidateDocument(path)`

Refetch a document from Firestore, and update the local cache. Useful if you want to update a given document without calling the connected `revalidate` function from use `useDocument` hook.

- Only argument is the Firestore document path (ex: `users/Fernando`)

## `revalidateCollection(path)`

Refetch a collection query from Firestore, and update the local cache. Useful if you want to update a given collection without calling the connected `revalidate` function from use `useCollection` hook.

- Only argument is the Firestore document path (ex: `users`)
- **Note** Calling `revalidateCollection` will update _all_ collection queries. If you're paginating data for a given collection, you probably won't want to use this function for that collection.

## `fuego`

The current firebase instance used by this library. Exports the following fields:

- `db`: the current firestore collection instance
- `auth`: the `firebase.auth` variable.

```js
import { fuego } from '@nandorojo/swr-firestore'

fuego.db.doc('users/Fernando').get()

fuego.auth().currentUser?.uid
```

## `getDocument(path, options?)`

If you don't want to use `useDocument` in a component, you can use this function outside of the React scope.

### Arguments

- **`path` required** The unique document path for your Firestore document.
- `options`
  - `ignoreFirestoreDocumentSnapshotField = true`. If `false`, it will return a `__snapshot` field too.
  - `parseDates`: An array of string keys that correspond to dates in your document. [Example](#parse-date-fields-in-your-documents).

### Returns

A promise with the firestore doc and some useful fields. See the [useDocument](#useDocument) `data` return type for more info.

## `getCollection(path, query?, options?)`

If you don't want to use `useCollection` in a component, you can use this function outside of the React scope.

### Arguments

- **`path` required** The unique collection path for your Firestore collection.
  - `ignoreFirestoreDocumentSnapshotField = true`. If `false`, it will return a `__snapshot` field too.
  - `parseDates`: An array of string keys that correspond to dates in your document. [Example](#parse-date-fields-in-your-documents).
- `query` refer to the second argument of [`useCollection`](#useCollection).
- `options`
  - `ignoreFirestoreDocumentSnapshotField = true`. If `false`, it will return a `__snapshot` field too in each document.
  - `parseDates`: An array of string keys that correspond to dates in your documents. [Example](#parse-date-fields-in-your-documents).

# Features

## TypeScript Support

Create a model for your `typescript` types, and pass it as a generic to `useDocument` or `useCollection`.

### useDocument

The `data` item will include your TypeScript model (or `null`), and will also include an `id` string, an `exists` boolean, and `hasPendingWrites` boolean.

```typescript
type User = {
  name: string
}

const { data } = useDocument<User>('users/fernando')

if (data) {
  const {
    id, // string
    name, // string
    exists, // boolean
    hasPendingWrites, // boolean
  } = data
}

const id = data?.id //  string | undefined
const name = data?.name // string | undefined
const exists = data?.exists // boolean | undefined
const hasPendingWrites = data?.hasPendingWrites // boolean | undefind
```

### useCollection

The `data` item will include your TypeScript model (or `null`), and will also include an `id` string.

```typescript
type User = {
  name: string
}

const { data } = useCollection<User>('users')

if (data) {
  data.forEach(({ id, name }) => {
    // ...
  })
}
```

## Shared global state between documents and collections

A great feature of this library is shared data between documents and collections. Until now, this could only be achieved with something like a verbose Redux set up.

So, what does this mean exactly?

Simply put, any documents pulled from a Firestore request will update the global cache.

**To make it clear, let's look at an example.**

Imagine you query a `user` document from Firestore:

```js
const { data } = useDocument('users/fernando')
```

And pretend that this document's `data` returns the following:

```json
{ "id": "fernando", "isHungry": false }
```

_Remember that `isHungry` is `false` here ^_

Now, let's say you query the `users` collection anywhere else in your app:

```js
const { data } = useCollection('users')
```

And pretend that this collection's `data` returns the following:

```json
[
  { "id": "fernando", "isHungry": true },
  {
    //...
  }
]
```

Whoa, `isHungry` is now true. But what happens to the original document query? Will we have stale data?

**Answer:** It will automatically re-render with the new data!

`swr-firestore` uses document `id` fields to sync any collection queries with existing document queries across your app.

That means that **if you somehow fetch the same document twice, the latest version will update everywhere.**

## License

MIT