Theo's Typesafe Cult•8mo ago

Best way to prefetch queries with tRPC and app/ dir

I am in the process of switching my pages/ T3 app to the new fancy app directory and know that React Query has a few ways to prefetch queries, and was wondering which one is the best for use with T3 app dir. 1. initialData The easiest, but also the most annoying in my eyes. You fetch the data on the server and then pass it down as initialData. 2. prefetchQuery & HydrationLayer Saw this in the docs but i’m not sure if it will work with the extended version of react-query that tRPC uses. 3. @tanstack/react-query-next-experimental This seems to be brand new, and I can’t really tell what’s different from the second option. Which method is best for prefetching on the server with T3 app dir?

Solution:

I think the main takeaway is: 1. prefetch the data using .prefetch() 2. dehydrate the state 3. pass the dehydrated state into react query 4. call .query(), which will pull from the cache instead of re-fetching...

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7 Replies

Endgame1013•8mo ago

I’ve used a setup like this before and it’s worked pretty well:

// MySSRComponent.tsx
import { createSSRHelper } from '@/server/api/ssr';
import ReactQueryHydrate from '@/components/ReactQueryHydrate';
import { dehydrate } from '@tanstack/react-query';

export default async function MySSRComponent() {
  // 1. create the server-side helper
  const helpers = await createSSRHelper();
  // 2. pre-fetch the tRPC procedure server-side
  await helpers.example.greeting.prefetch();
  // 3. get the dehydrated query client and pass it down to react-query's context provider
  const dehydratedState = dehydrate(helpers.queryClient);

  return (
    <ReactQueryHydrate state={dehydratedState}>
      <MyClientComponent />
    </ReactQueryHydrate>
  );
}
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// MyClientComponent.tsx
'use client';

import { api } from '@/lib/api';

export default function MyClientComponent() {
  const { data, status } = api.example.greeting.useQuery();

  if (status !== 'success') {
    // won't happen since the query has been prefetched
    return <div>Loading...</div>;
  }

  return (
    <pre>{JSON.stringify(data, null, 4)}</pre>
  );
}

// MySSRComponent.tsx
import { createSSRHelper } from '@/server/api/ssr';
import ReactQueryHydrate from '@/components/ReactQueryHydrate';
import { dehydrate } from '@tanstack/react-query';

export default async function MySSRComponent() {
  // 1. create the server-side helper
  const helpers = await createSSRHelper();
  // 2. pre-fetch the tRPC procedure server-side
  await helpers.example.greeting.prefetch();
  // 3. get the dehydrated query client and pass it down to react-query's context provider
  const dehydratedState = dehydrate(helpers.queryClient);

  return (
    <ReactQueryHydrate state={dehydratedState}>
      <MyClientComponent />
    </ReactQueryHydrate>
  );
}
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// MyClientComponent.tsx
'use client';

import { api } from '@/lib/api';

export default function MyClientComponent() {
  const { data, status } = api.example.greeting.useQuery();

  if (status !== 'success') {
    // won't happen since the query has been prefetched
    return <div>Loading...</div>;
  }

  return (
    <pre>{JSON.stringify(data, null, 4)}</pre>
  );
}

ethan•8mo ago

what does the ReactQueryHydrate component look like or is it just a client wrapper

Endgame1013•8mo ago

'use client';

import { Hydrate as RQHydrate, HydrateProps } from '@tanstack/react-query';

export default function ReactQueryHydrate(props: HydrateProps) {
  return <RQHydrate {...props} />;
}

'use client';

import { Hydrate as RQHydrate, HydrateProps } from '@tanstack/react-query';

export default function ReactQueryHydrate(props: HydrateProps) {
  return <RQHydrate {...props} />;
}

Solution

Endgame1013•8mo ago

ethan•8mo ago

yeah, makes sense thank you!!

yaba101•7mo ago

@Endgame1013 can we have repo for this, because I don't get the import { createSSRHelper } from '@/server/api/ssr'; implementation

Endgame1013•7mo ago

@yaba101, here is the code for that portion, sorry for the oversight:

import { appRouter } from './routes/_app';
import { createContext } from './context';
import { createServerSideHelpers } from '@trpc/react-query/server';
import superjson from 'superjson';

/**
 * SSR/RSC caller
 * @description use this function to create a TRPC server-side caller
 * @see https://trpc.io/docs/server/server-side-calls#create-caller
 */
export const createSSRCaller = async () => {
  return appRouter.createCaller(await createContext());
};

/**
 * Server-Side Helper
 * @description use this function to call tRPC procedures server-side and hydrate `react-query`'s cache
 * @see https://trpc.io/docs/client/nextjs/server-side-helpers#1-internal-router
 */
export const createSSRHelper = async () =>
  createServerSideHelpers({
    router: appRouter,
    ctx: await createContext(),
    transformer: superjson,
  });

import { appRouter } from './routes/_app';
import { createContext } from './context';
import { createServerSideHelpers } from '@trpc/react-query/server';
import superjson from 'superjson';

/**
 * SSR/RSC caller
 * @description use this function to create a TRPC server-side caller
 * @see https://trpc.io/docs/server/server-side-calls#create-caller
 */
export const createSSRCaller = async () => {
  return appRouter.createCaller(await createContext());
};

/**
 * Server-Side Helper
 * @description use this function to call tRPC procedures server-side and hydrate `react-query`'s cache
 * @see https://trpc.io/docs/client/nextjs/server-side-helpers#1-internal-router
 */
export const createSSRHelper = async () =>
  createServerSideHelpers({
    router: appRouter,
    ctx: await createContext(),
    transformer: superjson,
  });

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Best way to prefetch queries with tRPC and app/ dir