EventBus — UT2004

An in-process publish/subscribe event bus for UnrealScript on Unreal Tournament 2004. Pure script, no native code.

A UT99 / OldUnreal 469 port lives at eventbus-ut99.

Previously named EventGrid. It is a bus, not a grid — and the old name collided with Azure Event Grid. The UnrealScript package is now EventBus; mods still compiled against EventGrid.u need that package present at load until they are rebuilt.

Use it to decouple parts of a mod that would otherwise have to know about each other: something publishes an event on a topic, and whoever cares subscribes to it. Nothing needs a direct reference to anything else.

What you get

Publish:

local JsonObject Json;

Json = new class'JsonObject';
Json.AddString("PlayerName", "Cali");

EventBus.SendEvent("v1/player/connected", Json);

Subscribe — extend EventBusSubscriber, declare your topics, override ProcessEvent:

class MySubscriber extends EventBusSubscriber;

function ProcessEvent(string Topic, JsonObject EventData)
{
    log(Topic @ EventData.GetString("PlayerName"));
}

defaultproperties
{
    SubscriptionTopics(0)="v1/player/"    // prefix: matches connected, disconnected, chat, ...
}

Spawn it and it registers itself; destroy it and it unsubscribes. GetOrCreateEventBus() finds the bus (or creates it), so subscribers do not have to be wired up in any particular order.

Topic matching is by case-insensitive prefix, not exact match: subscribing to "v1/player/" receives "v1/player/chat". Subscribing to "" receives everything.

Install

Depends on JsonLib for the event payload. List both before your own package:

[Editor.EditorEngine]
EditPackages=JsonLib
EditPackages=EventBus
EditPackages=YourMod

The bus and its subscribers are Info actors — server-side only, so they do not need to go in ServerPackages.

Licence

MIT. Provided as-is, no support guarantee.