Channels (Pub/Sub)

Pulsabase Channels provide a dedicated pub/sub messaging layer for application events that aren’t tied to database mutations — things like typing indicators, cursor sharing, or real-time notifications.

Creating a Channel

TypeScript
Dart

import pb from './pulsabase';

const chat = pb.channel('chat-room-123');

// Subscribe to events on this channel
chat.on('message', (data) => {
  console.log(`${data.user}: ${data.message}`);
});

// Publish an event to all subscribers
chat.send('message', { user: 'Jane', message: 'Hello!' });

final chat = pb.channel('chat-room-123');

// Subscribe
chat.subscribe((data) => print(data));

// Publish
chat.publish({'user': 'Jane', 'message': 'Hello!'});

Use Cases

Use Case	Example Channel Name
Chat rooms	`chat-room-{roomId}`
Typing indicators	`typing-{roomId}`
Cursor sharing	`cursors-{documentId}`
Presence (who’s online)	`presence-{roomId}`
Push notifications	`notifications-{userId}`
Live polls	`poll-{pollId}`

Example: Typing Indicators

const room = pb.channel(`typing-${roomId}`);

// Broadcast that the current user is typing
async function onKeyPress() {
  const user = await pb.auth.getUser();
  room.send('typing', { userId: user.sub, name: user.given_name });
}

// Show typing indicator to other users
room.on('typing', ({ userId, name }) => {
  if (userId !== currentUserId) {
    showTypingIndicator(name);
  }
});

Example: Presence

const presence = pb.channel(`presence-${roomId}`);

// Announce join
const user = await pb.auth.getUser();
presence.send('join', { userId: user.sub, name: user.given_name });

// Track who's online
const onlineUsers = new Map();

presence.on('join', ({ userId, name }) => {
  onlineUsers.set(userId, name);
  renderOnlineList(onlineUsers);
});

presence.on('leave', ({ userId }) => {
  onlineUsers.delete(userId);
  renderOnlineList(onlineUsers);
});

// Broadcast leave on disconnect
window.addEventListener('beforeunload', () => {
  presence.send('leave', { userId: user.sub });
});

Channel Naming

Channel names are arbitrary strings. Choose a naming convention that makes sense for your application, typically using a type prefix and an identifier:

chat-{roomId}
doc-{documentId}
user-{userId}