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Data Transformers

You are able to serialize the response data & input args. The transformers need to be added both to the server and the client.

Using superjson​

SuperJSON allows us to transparently use e.g. standard Date/Map/Sets over the wire between the server and client. That means you can return any of these types in your API-resolver and use them in the client without recreating the objects from JSON.

How to​

1. Install​

yarn add superjson

2. Add to your initTRPC​

routers/router/_app.ts
import { initTRPC } from '@trpc/server';
import superjson from 'superjson';

export const t = initTRPC()({
  transformer: superjson,
});

3. Add to createTRPCClient() or setupTRPC()​

import { createTRPCClient } from '@trpc/client';
import superjson from 'superjson';
import type { AppRouter } from '~/server/routers/_app';

export const client = createTRPCClient<AppRouter>({
  transformer: superjson, // <--
  // [...]
});
utils/trpc.ts
import { setupTRPC } from '@trpc/next';
import superjson from 'superjson';
import type { AppRouter } from '~/server/routers/_app';

// [...]

export const trpc = setupTRPC<AppRouter>({
  config({ ctx }) {
    return {
      transformer: superjson, // <-- 
    };
  },
  // [...]
});

Different transformers for upload and download​

If a transformer should only be used for one directon or different transformers should be used for upload and download (e.g. for performance reasons), you can provide individual transformers for upload and download. Make sure you use the same combined transformer everywhere.

How to​

Here superjson is used for uploading and devalue for downloading data, because devalue is a lot faster but insecure to use on the server.

1. Install​

yarn add superjson devalue

2. Add to utils/trpc.ts​

utils/trpc.ts
import devalue from 'devalue';
import superjson from 'superjson';

// [...]

export const transformer = {
  input: superjson,
  output: {
    serialize: (object) => devalue(object),
    deserialize: (object) => eval(`(${object})`),
  },
};

3. Add to your AppRouter​

server/routers/_app.ts
import { initTRPC } from '@trpc/server';
import { transformer } from '../../utils/trpc';

export const t = initTRPC()({
  transformer,
});

export const appRouter = t.router({
  // [...]
});

4. Add to createTRPCClient()​

client.ts
import { createTRPCClient } from '@trpc/client';
import { transformer } from '../utils/trpc';

export const client = createTRPCClient<AppRouter>({
  transformer, // <--
  // [...]
});

DataTransformer interface​

type DataTransformer = {
  serialize(object: any): any;
  deserialize(object: any): any;
};

type CombinedDataTransformer = {
  input: DataTransformer;
  output: DataTransformer;
};