useTopic

Subscribes to a ROS topic for the lifetime of the calling component and re-renders on every incoming message. Automatically resubscribes whenever the topic name/type or other subscription options change, and unsubscribes on unmount.

import { useTopic } from "roshooks";

interface StringMsg {
  data: string;
}

const { message, topic } = useTopic<StringMsg>({
  name: "/chatter",
  messageType: "std_msgs/String",
});

Options

Option	Type	Default	Description
name	string	—	The topic name, e.g. "/chatter".
messageType	string	—	The message type, e.g. "std_msgs/String".
compression	string	"none"	"png", "cbor", "cbor-raw", or "none".
throttle_rate	number	0	Minimum time (ms) between messages.
queue_size	number	100	The bridge-side publish queue size.
latch	boolean	false	Latch the topic when publishing.
queue_length	number	0	The bridge-side subscribe queue length.
reconnect_on_close	boolean	true	Automatically resubscribe on reconnection.
enabled	boolean	true	Set to false to skip subscribing (e.g. while waiting on other state).

Returns

Field	Type	Description
message	TMessage | null	The latest message received, or null until the first one arrives (or when enabled is false).
topic	Topic<TMessage> | null	The underlying roslib.js Topic instance, or null while not subscribed.

Example

function ChatterLabel() {
  const { message } = useTopic<{ data: string }>({
    name: "/chatter",
    messageType: "std_msgs/String",
  });

  return <p>{message?.data ?? "(none)"}</p>;
}

Conditionally subscribing

const { message } = useTopic<StringMsg>({
  name: "/chatter",
  messageType: "std_msgs/String",
  enabled: isVisible,
});

See also usePublisher for publishing to a topic, and Global State with Jotai if you want a single shared subscription across many components instead of one per call site.