NativeMessenger

This is system-wide native messenger for Unity Entities. It provides an efficient way to trigger systems on demand without involving entities data or any structural changes.

Sending Messages

You can send values to messenger out of anywhere: burst, jobs or managed context.

Below is example of system that sends test messages every 4th update.

public partial struct SendTestSystem : ISystem
{
    private int _counter;

    public void OnUpdate(ref SystemState state)
    {
        if (_counter < 3)
        {
            _counter++;
        }
        else
        {
            _counter = 0;

            var messenger = SystemAPI.GetSingleton<Messenger>();
            messenger.Send(new TestMessage { value = 4.20f });
            messenger.Send(new TestMessage { value = 6.9f });
        }
    }
}

Receiving Messages

You can use both: SystemBase and ISystem based systems to react to messages:

Inheriting EventSystem

Below you can see an example of class based system which reacts to messages in different ways:

• If you certain that message is only one, you can use Message property
• If multiple messages of same type can be sent you can read all of them via Messages property.

public partial class TestClassSystem : EventSystem<TestMessage>
{
    protected override void OnUpdate()
    {
        Debug.Log(Message.value);
        foreach (var testMessage in Messages)
        {
            Debug.Log(testMessage.value);
        }
    }
}

Inheriting IEventSystem

Below you can see an example of ISystem based system.

[UpdateInGroup(typeof(NativeEventSystemGroup))]
public partial struct TestSystem : ISystem, IEventSystem<TestMessage>
{
    [Message] private NativeArray<TestMessage> _message;

    [BurstCompile]
    public void OnUpdate(ref SystemState state)
    {
        foreach (var testMessage in _message)
        {
            Debug.Log($"value: {testMessage.value}");
        }
    }
}

Unlike class based, ISystem requires [UpdateInGroup(typeof(NativeEventSystemGroup))] attribute in order to receive messages in proper system.

And in order to read messages it needs special attribute Message on a field. This field can only be one per system and can be used only one two types:

• Either TestMessage type directly

[Message] private TestMessage _message;

• Or NativeArray<TestMessage> if you need multiple

[Message] private NativeArray<TestMessage> _message;

• Or you may not use field at all if you only want to trigger OnUpdate without reading any data.