Data Sharing

The Pub/Sub API is accessible through the io.bus object.

See the JavaScript Pub/Sub example on GitHub.

By default, the Pub/Sub API is disabled. To enable it in your interop-enabled apps, set the bus property of the io.Connect configuration object to true when initializing the io.Connect library:

const config = { bus: true };

const io = await IODesktop(config);

To All Apps

To publish a message on a specific topic to all subscribed apps, use the publish() method. It accepts the message topic and the data to publish as arguments:

const topic = "stocks";
const data = { RIC: "AAPL.O" };

io.bus.publish(topic, data);

To Specific Apps

Use the MessageOptions object to make an app publish a message only to specific apps that have subscribed to a topic.

The MessageOptions object has the following properties, all of which are optional:

The example below demonstrates how to publish a message to another app (or to multiple instances of it) with a specific name:

const topic = "stocks";
const data = { RIC: "AAPL.O" };
const options = {
    target: {
        application: "client-portfolio"
    }
};

io.bus.publish(topic, data, options);

The Pub/Sub API compares the target property of the options argument with the identity of each app subscribed to the topic. It delivers the message only to subscribers with identity properties matching the respective properties of the target object.

The example below demonstrates how to publish messages with a specific routing key:

const topic = "stocks";
const data = { RIC: "AAPL.O" };
const options = {
    target: {
        routingKey: "portfolio"
    }
};

io.bus.publish(topic, data, options);

The Pub/Sub API delivers messages with a routingKey to all subscribers with the same routing key and to the ones with no routing key.

Messages from Any App

To subscribe for messages on a specific topic, use the subscribe() method. Upon successful subscription, it resolves with a Subscription object. Use the unsubscribe property of this object to stop receiving messages on that topic.

Provide the topic on which you want to receive messages and a callback to handle the messages:

const topic = "stocks";
const handler = (data, topic, source) => console.log(data, topic, source);

const { unsubscribe } = await io.bus.subscribe(topic, handler);

Messages from Specific Apps

Use the MessageOptions object to make an app subscribe for messages only from specific apps:

const topic = "stocks";
const handler = (data, topic, source) => console.log(data, topic, source);
const options = {
    target: {
        application: "instrument-list"
    }
};

const { unsubscribe } = await io.bus.subscribe(topic, handler, options);

The Pub/Sub API compares the target property of the options argument with the identity of the publisher. It invokes the callback only if all the properties of the target object match the respective properties of the identity of the publisher.

The example below demonstrates how to subscribe for messages with a specific routing key:

const topic = "stocks";
const handler = (data, topic, source) => console.log(data, topic, source);
const options = {
    target: {
        routingKey: "portfolio"
    }
};

const { unsubscribe } = await io.bus.subscribe(topic, handler, options);

The Pub/Sub API invokes the callback only for messages with a matching routing key and for the ones with no routing key.

For a complete list of the available Pub/Sub API methods and properties, see the Pub/Sub API Reference Documentation.