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tRPC End-to-End Type Safe APIs · Aula

Implementando assinaturas de dados em tempo real

Crie procedimentos de assinatura tRPC para enviar atualizações em tempo real do servidor aos clientes conectados.

Implementando assinaturas de dados em tempo real é uma aula grátis de tRPC End-to-End Type Safe APIs no CoddyKit. Esta é a aula 3 de 4. Você pode ler a aula completa abaixo gratuitamente — depois pratica ao vivo no navegador com um editor de código integrado e um tutor de IA 24/7. Faz parte do caminho de aprendizado de tRPC End-to-End Type Safe APIs, e seu progresso é sincronizado entre a web e o app CoddyKit. O curso de tRPC End-to-End Type Safe APIs inclui 4 aulas no total.

Partes desta aula ainda não foram traduzidas e aparecem em inglês.

Real-time Data with Subscriptions

Welcome to the final lesson on tRPC real-time! We've learned about WebSockets, now let's build live data features.

Subscriptions in tRPC allow your server to push real-time updates to connected clients. Unlike queries (which pull data) or mutations (which modify data), subscriptions are push-based.

  • Queries: Client asks, server responds once.
  • Mutations: Client sends data, server performs action, responds once.
  • Subscriptions: Client asks once, server sends updates over time.

Defining Server Subscriptions

To create a subscription on your tRPC server, you use the createSubscription helper, similar to createQuery or createMutation.

A key difference is that a subscription procedure returns an observable. An observable is a stream of data that can emit multiple values over time.

Let's look at the basic structure.

The Observable Pattern

When defining a subscription, you'll use an observable pattern. This involves a function that receives an emit function and returns a cleanup function.

  • The emit function is what you call to send data to clients.
  • The cleanup function (returned by your subscription logic) runs when a client unsubscribes.

This allows you to manage resources like event listeners or intervals.

Server Code: Basic Live Counter

Here's a simple tRPC server-side subscription that emits a number every second. This number could represent anything, like a live user count.

import { router, publicProcedure } from './trpc';
import { observable } from '@trpc/server/observable';

export const appRouter = router({
  onUpdate: publicProcedure.subscription(() => {
    // This is where we create the observable
    return observable<number>((emit) => {
      let count = 0;
      const interval = setInterval(() => {
        count++;
        emit.next(count); // Push new data to clients
      }, 1000);

      // Return a cleanup function
      return () => {
        clearInterval(interval);
      };
    });
  }),
});

// This code is illustrative and not directly runnable
// without a full Node.js server setup.
// For context, 'router' and 'publicProcedure' would be
// initialized from '@trpc/server'.

Understanding the Server Flow

In the previous example:

  • publicProcedure.subscription(() => {...}) defines the subscription endpoint.
  • observable((emit) => {...}) creates a data stream that will send number types.
  • emit.next(count) is called repeatedly inside setInterval to push the current count to all subscribed clients.
  • The returned function () => { clearInterval(interval); } ensures the interval stops when a client disconnects or unsubscribes, preventing memory leaks.

Consuming Subscriptions on the Client

On the client-side, tRPC provides a convenient hook for consuming subscriptions, typically trpc.useSubscription if you're using React Query.

This hook works similarly to useQuery but maintains an open connection and updates your component whenever new data arrives from the server.

Client Code: React Component Example

Here's a React component that subscribes to our onUpdate procedure and displays the live counter. Notice how data updates automatically.

import React from 'react';

// Mock tRPC client for runnable example
const mockTRPCClient = {
  onUpdate: {
    subscribe: (opts) => {
      let count = 0;
      const interval = setInterval(() => {
        count++;
        opts.onData(count); // Simulate server pushing data
      }, 1000);
      return { // Return unsubscribe function
        unsubscribe: () => clearInterval(interval),
      };
    },
  },
};

// Mock useSubscription hook
const useSubscription = (path, input, { onData, onError }) => {
  React.useEffect(() => {
    const subscription = mockTRPCClient[path].subscribe({
      onData,
      onError,
    });
    return () => subscription.unsubscribe();
  }, [path, input, onData, onError]);
};

function LiveCounter() {
  const [currentCount, setCurrentCount] = React.useState(0);

  useSubscription(
    'onUpdate', // Path to your tRPC subscription
    undefined,  // No input for this subscription
    {
      onData(data) {
        setCurrentCount(data); // Update state with new data
      },
      onError(err) {
        console.error('Subscription error:', err);
      },
    }
  );

  return (
    <div>
      <h3>Live Counter:</h3>
      <p>Current value: <b>{currentCount}</b></p>
    </div>
  );
}

// This would be rendered by a framework like React.
// For runnable purposes, we can simulate a main entry point.
export default function Main() {
  return <LiveCounter />;
}

Subscriptions with Input

Just like queries and mutations, subscriptions can accept input. This is incredibly useful for filtering or customizing the data stream for each client.

For example, you might subscribe to updates for a specific productId or a particular chat roomName.

You'll define the input schema using Zod on the server and pass the input object on the client.

Code: Subscription with Input

Here's how you'd define a subscription that takes a topic string as input on the server, and how a client would use it.

/* --- SERVER-SIDE (Illustrative) --- */
import { z } from 'zod';
import { router, publicProcedure } from './trpc';
import { observable } from '@trpc/server/observable';

export const appRouterWithInput = router({
  onTopicUpdate: publicProcedure
    .input(z.object({ topic: z.string() })) // Define input schema
    .subscription(({ input }) => {
      return observable<string>((emit) => {
        // Simulate updates for a specific topic
        const interval = setInterval(() => {
          emit.next(`Update for '${input.topic}': ${Date.now()}`);
        }, 2000);
        return () => clearInterval(interval);
      });
    }),
});

/* --- CLIENT-SIDE (React Component) --- */
import React from 'react';

// Mock tRPC client for runnable example
const mockTRPCClientWithInput = {
  onTopicUpdate: {
    subscribe: (input, opts) => {
      const interval = setInterval(() => {
        opts.onData(`Update for '${input.topic}': ${Date.now()}`);
      }, 2000);
      return {
        unsubscribe: () => clearInterval(interval),
      };
    },
  },
};

// Mock useSubscription hook for runnable example
const useSubscriptionWithInput = (path, input, { onData, onError }) => {
  React.useEffect(() => {
    const subscription = mockTRPCClientWithInput[path].subscribe(
      input,
      { onData, onError }
    );
    return () => subscription.unsubscribe();
  }, [path, input, onData, onError]);
};

function TopicUpdates({ topic }) {
  const [latestUpdate, setLatestUpdate] = React.useState('');

  useSubscriptionWithInput(
    'onTopicUpdate', 
    { topic }, // Pass the input object
    {
      onData(data) {
        setLatestUpdate(data);
      },
      onError(err) {
        console.error('Subscription error:', err);
      },
    }
  );

  return (
    <div>
      <h4>Topic: {topic}</h4>
      <p>{latestUpdate}</p>
    </div>
  );
}

export default function Main() {
  return (
    <div>
      <TopicUpdates topic="news" />
      <TopicUpdates topic="sports" />
    </div>
  );
}

Best Practices for Subscriptions

When working with tRPC subscriptions, consider these best practices:

  • Cleanup: Always return a cleanup function from your observable to release resources (e.g., clear intervals, close database connections).
  • Error Handling: Implement onError callbacks on the client to gracefully handle subscription errors.
  • Rate Limiting: Be mindful of how frequently you emit data to avoid overwhelming clients or your server.
  • When to Use: Subscriptions are great for truly real-time data. For less critical updates, traditional queries with polling or client-side caching might be sufficient.
  • Authentication/Authorization: Use tRPC middleware to protect subscription procedures, ensuring only authorized users receive updates.

Quick Check: Subscription Basics

You've defined a tRPC subscription that emits a string every 5 seconds. Which part of the client-side useSubscription hook would you use to process each incoming string?

Recap: Live Data Subscriptions

In this lesson, you've learned to implement live data subscriptions with tRPC:

  • Server-side: Define subscription procedures using publicProcedure.subscription and return an observable.
  • Observable Logic: Use the emit.next() function to push data and return a cleanup function.
  • Client-side: Consume subscriptions using trpc.useSubscription, providing an onData callback to handle incoming real-time updates.
  • Input: Pass arguments to subscriptions for filtered or customized data streams.

Congratulations! You can now build powerful real-time features with tRPC's end-to-end type safety.

Perguntas Frequentes

A aula “Implementando assinaturas de dados em tempo real” é grátis?

Sim — o texto completo de “Implementando assinaturas de dados em tempo real” é grátis para ler aqui na web. Para praticá-la interativamente (um editor de código integrado e um tutor de IA 24/7) e desbloquear o restante do curso de tRPC End-to-End Type Safe APIs, atualize para CoddyKit PRO. O curso de tRPC End-to-End Type Safe APIs inclui 4 aulas no total.

O que vou aprender em “Implementando assinaturas de dados em tempo real”?

Crie procedimentos de assinatura tRPC para enviar atualizações em tempo real do servidor aos clientes conectados. Você pratica tRPC End-to-End Type Safe APIs com código prático que executa diretamente no navegador, e um tutor de IA 24/7 responde suas dúvidas enquanto trabalha na aula.

Preciso ter experiência prévia para começar tRPC End-to-End Type Safe APIs?

Nenhuma experiência prévia é necessária. tRPC End-to-End Type Safe APIs no CoddyKit é estruturado para alunos iniciantes até avançados, então você pode começar aqui ou desde o início e aprender no seu ritmo. Esta é a aula 3 de 4.

Quanto tempo leva a aula “Implementando assinaturas de dados em tempo real”?

A maioria das aulas CoddyKit leva cerca de 5–10 minutos. Cada uma é compacta e interativa, então você faz progresso constante e retoma exatamente de onde parou entre web e app.

Posso escrever e executar código nesta aula de tRPC End-to-End Type Safe APIs?

Sim. Cada aula de tRPC End-to-End Type Safe APIs inclui um editor de código integrado, então você escreve e executa código real direto no navegador e recebe feedback de IA instantaneamente — nenhuma configuração local necessária.

Todas as aulas deste curso

  1. Introdução ao tempo real com tRPC
  2. Configurando WebSockets para assinaturas
  3. Implementando assinaturas de dados em tempo real
  4. Tratamento de reconexão e limpeza de assinaturas
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