Method HasSingleton

HasSingleton<T>()

Checks whether a singleton component of the specified type exists.

Declaration

public static bool HasSingleton<T>() where T : unmanaged

Returns

Type	Description
bool	True, if a singleton of the specified type exists in the current World.

Type Parameters

Name	Description
T	The IComponentData subtype of the singleton component. This component type must not implement IEnableableComponent

Remarks

The SystemAPI singleton methods build their query with the default EntityQueryOptions flags, which exclude entities that have the Disabled component and entities that have the Prefab component. So if the only entity that has component T is disabled or is an entity prefab, this method returns false, and GetSingleton<T>() throws an exception.

To find a singleton component on a disabled entity or on an entity prefab, create an EntityQuery with the IncludeDisabledEntities or IncludePrefab option, then call HasSingleton<T>() on that query.

Exceptions

Type	Condition
InvalidOperationException	Thrown if T implements IEnableableComponent and if safety checks are enabled.
InvalidOperationException	Thrown if more than one entity has component T and if safety checks are enabled.