# Trigger Subscriptions

Now that clients can subscribe to a field, you will need to notify Lighthouse when the underlying data has changed.

# Broadcast Directive

The @broadcast directive will broadcast all updates to the Post model to the postUpdated subscription.

type Mutation {
  updatePost(input: UpdatePostInput!): Post
    @broadcast(subscription: "postUpdated")

You can reference the same subscription from multiple fields, or vice-versa trigger multiple subscriptions from a single field.

# Fire Subscriptions From Code

The Subscription class offers a utility method broadcast that can be used to broadcast subscriptions from anywhere in your application.

It accepts three parameters:

  • string $subscriptionField The name of the subscription field you want to trigger
  • mixed $root The result object you want to pass through
  • bool $shouldQueue = null Optional, overrides the default configuration lighthouse.subscriptions.queue_broadcasts

The following example shows how to trigger a subscription after an update to the Post model.

$post->title = $newTitle;

\Nuwave\Lighthouse\Execution\Utils\Subscription::broadcast('postUpdated', $post);