# Set up with React Server Components

> 

> [!WARNING] Deprecated
> The classic React Query integration (`@trpc/react-query`) only gets bug fixes, and will be removed in the next major version of tRPC. New projects should use the [TanStack React Query integration](https://trpc.io/docs/client/tanstack-react-query/server-components.md) (`@trpc/tanstack-react-query`). To move an existing project, follow the [migration guide](https://trpc.io/docs/client/tanstack-react-query/migrating.md).


> [!TIP]
> **Using Next.js?** See the dedicated [Next.js App Router setup guide](https://trpc.io/docs/client/nextjs/app-router-setup.md) for the recommended approach.


This guide is an overview of how one may use tRPC with a React Server Components (RSC) framework such as Next.js App Router.
Be aware that RSC on its own solves a lot of the same problems tRPC was designed to solve, so you may not need tRPC at all.

There is also not a one-size-fits-all way to integrate tRPC with RSCs, so see this guide as a starting point and adjust it
to your needs and preferences.

> [!NOTE] Info
> If you're looking for how to use tRPC with Server Actions, see the [Server Actions guide](https://trpc.io/docs/client/nextjs/server-actions.md).


> [!WARNING] Caution
> Please read React Query's [Advanced Server Rendering](https://tanstack.com/query/latest/docs/framework/react/guides/advanced-ssr) docs before proceeding to understand the different types of server rendering
> and what footguns to avoid.


## Add tRPC to existing projects

### 1. Install deps

```package-install
@trpc/server @trpc/client @trpc/react-query @tanstack/react-query@latest zod client-only server-only
```

### 2. Create a tRPC router

Initialize your tRPC backend in `trpc/init.ts` using the `initTRPC` function, and create your first router. We're going to make a simple "hello world" router and procedure here - but for deeper information on creating your tRPC API you should refer to the [Quickstart guide](https://trpc.io/docs/quickstart.md) and [Backend usage docs](https://trpc.io/docs/server/overview.md) for tRPC information.

> [!NOTE] Info
> The file names used here are not enforced by tRPC. You may use any file structure you wish.


<details>
<summary>View sample backend</summary>

```ts title="trpc/init.ts"
import { initTRPC } from '@trpc/server';
import { cache } from 'react';

export const createTRPCContext = cache(async () => {
  /**
   * @see: https://trpc.io/docs/server/context
   */
  return { userId: 'user_123' };
});

// Avoid exporting the entire t-object
// since it's not very descriptive.
// For instance, the use of a t variable
// is common in i18n libraries.
const t = initTRPC.create({
  /**
   * @see https://trpc.io/docs/server/data-transformers
   */
  // transformer: superjson,
});

// Base router and procedure helpers
export const createTRPCRouter = t.router;
export const createCallerFactory = t.createCallerFactory;
export const baseProcedure = t.procedure;
```

<br />

```ts title="trpc/routers/_app.ts"
import { z } from 'zod';
import { baseProcedure, createTRPCRouter } from '../init';

export const appRouter = createTRPCRouter({
  hello: baseProcedure
    .input(
      z.object({
        text: z.string(),
      }),
    )
    .query((opts) => {
      return {
        greeting: `hello ${opts.input.text}`,
      };
    }),
});

// export type definition of API
export type AppRouter = typeof appRouter;
```

<br />

> [!NOTE]
> The backend adapter depends on your framework and how it sets up API routes. The following example sets up GET and POST routes at `/api/trpc/*` using the [fetch adapter](https://trpc.io/docs/server/adapters/fetch.md) in Next.js.


```ts title="app/api/trpc/[trpc]/route.ts"
import { fetchRequestHandler } from '@trpc/server/adapters/fetch';
import { createTRPCContext } from '../../../../trpc/init';
import { appRouter } from '../../../../trpc/routers/_app';

const handler = (req: Request) =>
  fetchRequestHandler({
    endpoint: '/api/trpc',
    req,
    router: appRouter,
    createContext: createTRPCContext,
  });

export { handler as GET, handler as POST };
```

</details>

### 3. Create a Query Client factory

Create a shared file `trpc/query-client.ts` that exports a function that creates a `QueryClient` instance.

```ts title="trpc/query-client.ts"
import {
  defaultShouldDehydrateQuery,
  QueryClient,
} from '@tanstack/react-query';
import superjson from 'superjson';

export function makeQueryClient() {
  return new QueryClient({
    defaultOptions: {
      queries: {
        staleTime: 30 * 1000,
      },
      dehydrate: {
        // serializeData: superjson.serialize,
        shouldDehydrateQuery: (query) =>
          defaultShouldDehydrateQuery(query) ||
          query.state.status === 'pending',
      },
      hydrate: {
        // deserializeData: superjson.deserialize,
      },
    },
  });
}
```

We're setting a few default options here:

- `staleTime`: With SSR, we usually want to set some default staleTime above 0 to avoid refetching immediately on the client.
- `shouldDehydrateQuery`: This is a function that determines whether a query should be dehydrated or not. Since the RSC transport protocol
  supports hydrating promises over the network, we extend the `defaultShouldDehydrateQuery` function to also include queries that are
  still pending. This will allow us to start prefetching in a server component high up the tree, then consuming that promise in a client component further down.
- `serializeData` and `deserializeData` (optional): If you set up a [data transformer](https://trpc.io/docs/server/data-transformers.md) in the previous step, set this option
  to make sure the data is serialized correctly when hydrating the query client over the server-client boundary.

### 4. Create a tRPC client for Client Components

The `trpc/client.tsx` is the entrypoint when consuming your tRPC API from client components. In here, import the **type definition** of
your tRPC router and create typesafe hooks using `createTRPCReact`. We'll also export our context provider from this file.

```tsx title="trpc/client.tsx"
'use client';

// ^-- to make sure we can mount the Provider from a server component
import type { QueryClient } from '@tanstack/react-query';
import { QueryClientProvider } from '@tanstack/react-query';
import { httpBatchLink } from '@trpc/client';
import { createTRPCReact } from '@trpc/react-query';
import React, { useState } from 'react';
import { makeQueryClient } from './query-client';
import type { AppRouter } from './routers/_app';

export const trpc = createTRPCReact<AppRouter>();

let clientQueryClientSingleton: QueryClient;
function getQueryClient() {
  if (typeof window === 'undefined') {
    // Server: always make a new query client
    return makeQueryClient();
  }
  // Browser: use singleton pattern to keep the same query client
  return (clientQueryClientSingleton ??= makeQueryClient());
}

function getUrl() {
  const base = (() => {
    if (typeof window !== 'undefined') return '';
    if (process.env.VERCEL_URL) return `https://${process.env.VERCEL_URL}`;
    return 'http://localhost:3000';
  })();
  return `${base}/api/trpc`;
}

export function TRPCProvider(
  props: Readonly<{
    children: React.ReactNode;
  }>,
) {
  // NOTE: Avoid useState when initializing the query client if you don't
  //       have a suspense boundary between this and the code that may
  //       suspend because React will throw away the client on the initial
  //       render if it suspends and there is no boundary
  const queryClient = getQueryClient();

  const [trpcClient] = useState(() =>
    trpc.createClient({
      links: [
        httpBatchLink({
          // transformer: superjson, <-- if you use a data transformer
          url: getUrl(),
        }),
      ],
    }),
  );

  return (
    <trpc.Provider client={trpcClient} queryClient={queryClient}>
      <QueryClientProvider client={queryClient}>
        {props.children}
      </QueryClientProvider>
    </trpc.Provider>
  );
}
```

Mount the provider in the root of your application (e.g. `app/layout.tsx` when using Next.js).

### 5. Create a tRPC caller for Server Components

To prefetch queries from server components, we use a tRPC caller. The `@trpc/react-query/rsc` module exports a thin wrapper around
[`createCaller`](https://trpc.io/docs/server/server-side-calls.md) that integrates with your React Query client.

```tsx title="trpc/server.tsx"
import 'server-only'; // <-- ensure this file cannot be imported from the client

import { createHydrationHelpers } from '@trpc/react-query/rsc';
import { cache } from 'react';
import { createCallerFactory, createTRPCContext } from './init';
import { makeQueryClient } from './query-client';
import { appRouter } from './routers/_app';

// IMPORTANT: Create a stable getter for the query client that
//            will return the same client during the same request.
export const getQueryClient = cache(makeQueryClient);
const caller = createCallerFactory(appRouter)(createTRPCContext);

export const { trpc, HydrateClient } = createHydrationHelpers<typeof appRouter>(
  caller,
  getQueryClient,
);
```

## Using your API

Now you can use your tRPC API in your app. While you can use the React Query hooks in client components just like you would in any other React app,
we can take advantage of the RSC capabilities by prefetching queries in a server component high up the tree. You may be familiar with this
concept as "render as you fetch" commonly implemented as loaders. This means the request fires as soon as possible but without suspending until
the data is needed by using the `useSuspenseQuery` hook.

Read a prefetch you don't `await` with `useSuspenseQuery` ([Leveraging Suspense](#leveraging-suspense)): with `useQuery`, the server can render the loading state while the browser already has the data, and React reports a hydration mismatch.
For a component on `useQuery`, like the one below, `await` the `prefetch` call instead.

```tsx title="app/page.tsx"
import { trpc, HydrateClient } from '../trpc/server';
import { ClientGreeting } from './client-greeting';

export default async function Home() {
  await trpc.hello.prefetch();

  return (
    <HydrateClient>
      <div>...</div>
      {/** ... */}
      <ClientGreeting />
    </HydrateClient>
  );
}
```

```tsx title="app/client-greeting.tsx"
'use client';

// <-- hooks can only be used in client components
import { trpc } from '../trpc/client';

export function ClientGreeting() {
  const greeting = trpc.hello.useQuery();
  if (!greeting.data) return <div>Loading...</div>;
  return <div>{greeting.data.greeting}</div>;
}
```

### Leveraging Suspense

You may prefer handling loading and error states using Suspense and Error Boundaries. You can do this by using the `useSuspenseQuery` hook.

```tsx title="app/page.tsx"
import { trpc, HydrateClient } from '../trpc/server';
import { Suspense } from 'react';
import { ErrorBoundary } from 'react-error-boundary';
import { ClientGreeting } from './client-greeting';

export default async function Home() {
  void trpc.hello.prefetch();

  return (
    <HydrateClient>
      <div>...</div>
      {/** ... */}
      <ErrorBoundary fallback={<div>Something went wrong</div>}>
        <Suspense fallback={<div>Loading...</div>}>
          <ClientGreeting />
        </Suspense>
      </ErrorBoundary>
    </HydrateClient>
  );
}
```

```tsx title="app/client-greeting.tsx"
'use client';

import { trpc } from '../trpc/client';

export function ClientGreeting() {
  const [data] = trpc.hello.useSuspenseQuery();
  return <div>{data.greeting}</div>;
}
```

### Getting data in a server component

If you need access to the data in a server component, you can invoke the procedure directly instead of using `.prefetch()`, just like you use
[the normal server caller](https://trpc.io/docs/server/server-side-calls.md). Please note that this method is detached from your query client and does not
store the data in the cache. This means that you cannot use the data in a server component and expect it to be available in the client. This is
intentional and explained in more detail in the [Advanced Server Rendering](https://tanstack.com/query/latest/docs/framework/react/guides/advanced-ssr#data-ownership-and-revalidation)
guide.

```tsx title="app/page.tsx"
import { trpc } from '../trpc/server';

export default async function Home() {
  // Use the caller directly without using `.prefetch()`
  const greeting = await trpc.hello();

  return <div>{greeting.greeting}</div>;
}
```