Signals and notifications

Send a signal to a running graph. Receive a notification from the service. The complete Engine example shows both with setup and cleanup.

SoundSignalId

Find an ID with eventAsset.GetSignalId("Horn"). It remembers a declared signal’s name, slot, and stable identity. IsValid is false for a default or unresolved ID. You cannot call its internal constructor from normal gameplay code.

Name is the remembered name. Equals(SoundSignalId) and Equals(object) compare stable identities, or case-sensitive names when no identity exists. GetHashCode follows that identity; ToString returns the name.

Resolve a declared signal · excerpt

if (SoundBus.TryResolve(Sounds.Engine, out var sound))
{
    var horn = sound.GetSignalId("Horn");
    if (horn.IsValid)
        SoundBus.SendSignal(engine, horn);
}

This excerpt needs a retained Engine handle engine. Cache the resolved ID if you send it repeatedly. Signal execution happens on the next service update, subject to the play still being able to process it. The string overload matches the exact authored name. The event needs an On Signal node and must still be alive.

SoundSignalId · declared members

public readonly string Name
public bool IsValid { get; }
public bool Equals(SoundSignalId other)
public override bool Equals(object obj)
public override int GetHashCode()
public override string ToString()

SoundNotifications

Access the shared channel through SoundBus.Notifications; its constructor is internal.

Subscribe(Action<SoundNotification> listener) adds a callback and returns an IDisposable token. Dispose it to remove the callback. A null listener throws ArgumentNullException. The same delegate is not added twice; the returned tokens refer to the same subscription, so disposing either removes it. Different lambda instances count as different delegates.

Unsubscribe(listener) removes that delegate and returns true if it was registered, false otherwise, including for null. ListenerCount reports the number of callbacks currently subscribed. A callback throwing an exception is logged without preventing the other callbacks from running.

SoundNotifications · declared members

public int ListenerCount { get; }
public IDisposable Subscribe(Action<SoundNotification> listener)
public bool Unsubscribe(Action<SoundNotification> listener)

Subscribe in OnEnable, dispose in OnDisable, and keep callbacks short. The bus follows a manager replacement within the session. A new Unity play session clears subscriptions. Direct ISoundService.Notification subscriptions belong to that service instance and must be removed from the same instance.

SoundNotification

Field	Meaning
Handle	The play that changed state. Filter by it to ignore other sounds.
Kind	Which stage is being reported.
Reason	Failure/cancellation reason, otherwise Accepted.
Sound	The played event asset.
Owner	The original owner, still reported after owner loss.
EventId	The event’s identity.
Revision	The event revision used for this play.
IsTerminal	True for Finished, Cancelled, or Failed.

The constructor packages those fields in the order shown in its signature. Consumer code normally receives these records rather than constructing them. Constructing one does not send it to listeners.

SoundNotification · declared members

public readonly SoundHandle Handle
public readonly SoundNotificationKind Kind
public readonly SoundPlayStatus Reason
public readonly SoundEvent Sound
public readonly SoundOwnerToken Owner
public readonly string EventId
public readonly string Revision
public SoundNotification(SoundHandle handle, SoundNotificationKind kind, SoundPlayStatus reason, SoundEvent sound, SoundOwnerToken owner, string eventId, string revision)
public bool IsTerminal { get; }

SoundNotificationKind

Kind	Meaning
Accepted	A play was admitted, possibly still waiting.
Started	Its graph began running. This does not promise the first voice is already audible.
Finished	The play ended naturally.
Cancelled	A stop, graph ending operation, or replacement ended it. A normal stop can have reason Accepted.
Failed	An admitted play could not start or continue. Read Reason.

SoundNotificationKind · declared members

Accepted
Started
Finished
Cancelled
Failed

The built-in service delivers queued notifications at the end of its update on the main thread, after advancing graph work. They are observations, not a way to modify the graph midway through a step. Immediate rejected requests usually have no notification because they never became a play; always inspect the original result too.

Read every result and notification for startup failures, End Event cancellation, replacement, and callback delivery order.