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Channel Class

The Channel class implements an push channel and

  • Constructs a CometD channel path based on the provided scope.
  • Automatically reuses existing subscriptions for the same path if available.
  • Provides methods to publish data to the channel and to subscribe/unsubscribe from it.
  • Supports automatic cleanup of duplicate subscriptions.
Class signature
export default class Channel {
    constructor(scope: ChannelScope)
    publish(content: FIXME): Promise<Message | Message[]>
    subscribe(update: (data: unknown) => unknown, options?: { inert?: boolean }): Promise<SubscriptionHandle>
    unsubscribe(): Promise<void>
    unsubscribeAll(): Promise<void>
}

Properties​

  • path (string): The computed CometD channel path based on the scope.
  • update (Callback | undefined): A callback function invoked when a message is received.
  • subscription (SubscriptionHandle | null): The current active CometD subscription handle, if any.

Constructor​

Constructs the channel path using the provided scope. If a subscription already exists for this path, it is reused.

Definition
constructor(scope: ChannelScope)
  • scope (ChannelScope object): An object defining the channel’s namespace, including:
    • scopeBoundary: Entity type
    • scopeKey: Instance key (GUID)
    • pushCategory: Define the type of the push channel. Takes a value of the PUSH_CATEGORY enum.
learn more

To learn about scope properties, read Defining scope.

Methods​

Publish​

Publishes a message to the channel. Returns a promise resolving to one or more published messages.

Definition
publish(content: FIXME): Promise<Message | Message[]>

Parameters​

  • content (FIXME): The content to be published.

Subscribe​

Returns the SubscriptionHandle from CometD. Subscribes to the channel and sets the update handler.

Definition
subscribe(update: (data: unknown) => unknown, options?: { inert?: boolean }): Promise<SubscriptionHandle>

Parameters​

  • update: Callback to run when a new message is received.
  • options ({ inert?: boolean }, optional): Additional options (e.g. inert to suppress handlers).
Example
import { Channel, authAdapter, SCOPE_BOUNDARY, PUSH_CATEGORY } from 'epicenter-libs';

const session = authAdapter.getLocalSession();
const channel = new Channel({
    scopeBoundary: SCOPE_BOUNDARY.GROUP,
    scopeKey: session.groupKey,
    pushCategory: PUSH_CATEGORY.CHAT,
});

channel.subscribe((data) => {
    console.log(data.content);
});

Unsubscribe​

Removes the current subscription from CometD and clears the subscription handle.

Definition
unsubscribe(): Promise<void>

Unsubscribe all​

Removes all existing subscriptions from the CometD adapter.

Definition
unsubscribeAll(): Promise<void>