Class EntityQueryManagedComponentExtensions

Inheritance
Object
EntityQueryManagedComponentExtensions
Namespace: Unity.Entities
Syntax
public static class EntityQueryManagedComponentExtensions

Methods

GetSingleton<T>(EntityQuery)

Gets the value of a singleton component.

Declaration
public static T GetSingleton<T>(this EntityQuery query)
    where T : class, IComponentData
Parameters
Type Name Description
EntityQuery query
Returns
Type Description
T

A copy of the singleton component.
Type Parameters
Name Description
T

The component type.
Remarks

A singleton component is a component of which only one instance exists that satisfies this query.

Exceptions
Type Condition
InvalidOperationException
See Also

SetSingleton<T>(EntityQuery, T)

Sets the value of a singleton component.

Declaration
public static void SetSingleton<T>(this EntityQuery query, T value)
    where T : class, IComponentData
Parameters
Type Name Description
EntityQuery query
T value

An instance of type T containing the values to set.
Type Parameters
Name Description
T

The component type.
Remarks

For a component to be a singleton, there can be only one instance of that component that satisfies this query.

Note: singletons are otherwise normal entities. The EntityQuery and ComponentSystemBase singleton functions add checks that you have not created two instances of a type that can be accessed by this singleton query, but other APIs do not prevent such accidental creation.

To create a singleton, create an entity with the singleton component.

For example, if you had a component defined as:

    public struct Singlet : IComponentData
{
   public int Value;
}

You could create a singleton as follows:

       Entity singletonEntity = entityManager.CreateEntity(typeof(Singlet));
       entityManager.SetComponentData(singletonEntity, new Singlet { Value = 1 });

To update the singleton component after creation, you can use an EntityQuery object that selects the singleton entity and call this SetSingleton() function:

            queryForSingleton.SetSingleton<Singlet>(new Singlet {Value = 1});

You can set and get the singleton value from a system: see SetSingleton<T>(T) and GetSingleton<T>().

Exceptions
Type Condition
InvalidOperationException

Thrown if more than one instance of this component type exists in the world or the component type appears in more than one archetype.
See Also