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Decorators & Metadata

What is a Decorator?​

A TypeScript decorator is a function that attaches behavior or metadata to classes, methods, or parameters. In OpenCore, decorators are the primary way to declare runtime behavior:

  • @Controller() → "this class is a controller"
  • @OnNet('event:name') → "this method handles a net event"
  • @Command({ ... }) → "this method is a command"

Decorators describe intent. The framework turns that intent into runtime bindings during bootstrap.

Import Style​

OpenCore supports both styles:

  • Direct imports (common in framework internals and tests): @Controller(), @OnNet(), @Command().
  • Namespace style (still supported): @Server.Controller(), @Client.OnNet(), etc.

In this documentation, examples mostly use direct imports for brevity.

Why decorators?​

Without decorators, most multiplayer server codebases drift into hidden globals, ad-hoc event registration, and duplicated validation. OpenCore decorators solve this by:

  • Making entry points explicit (controllers)
  • Centralizing binding into the bootstrap phase
  • Making security and validation declarative

When do decorators execute?​

1. Decorator evaluation (module load time)​

Decorators execute when the module is imported. If a module is never imported, its decorators never run and the framework cannot discover it.

2. Framework binding (bootstrap scan)​

After decorators store metadata, the framework becomes "live" only after the bootstrap scan during init() / init().

Key rule: If a controller is not imported before bootstrap scanning, it does not exist for the framework.

Guarantees​

Decorators provide a stable contract:

  • Consistent entry points — handlers receive a Player context where required
  • Centralized validation and security — schemas and security decorators run before your logic
  • Explicit runtime wiring — you can reason about behavior by reading the controller class

Server Decorators​

Class Decorators​

DecoratorDescription
@Controller()Marks a class as a server-side controller. Entry point for commands, events, and handlers.
@Service()Marks a class as a reusable service (business logic). Singleton by default.
@Bind()Registers a class in the DI container. For utilities, adapters, or low-level classes.
@Repo()Semantic alias for @Bind(). Intended for data access layers.

Method Decorators​

DecoratorDescription
@Command()Registers a chat/console command handler with argument parsing and validation.
@OnNet()Subscribes to a network event (client → server).
@OnTick()Executes on every server tick. Use for lightweight, high-frequency logic.
@OnFrameworkEvent()Listens to internal framework lifecycle events.
@OnRuntimeEvent()Subscribes to native FiveM events (playerJoining, playerDropped, etc.).
@RequiresState()Ensures the player is in a specific state before execution.
@Throttle()Rate-limits the method per player or context.
@Export()Exposes the method as a resource export for inter-resource APIs through the active adapter.
@Guard()Applies access control (permissions, roles, ranks) before execution.
@Public()Marks the method as explicitly public, bypassing guards.

Client Decorators​

Class Decorators​

DecoratorDescription
@Controller()Marks a class as a client-side controller for UI, input, and client events.
@Service()Marks a class as a reusable client-side service for shared business logic.

Method Decorators​

DecoratorDescription
@OnNet()Subscribes to a network event (server → client).
@LocalEvent()Subscribes to a local (client-only) event for internal communication.
@OnGameEvent()Listens to GTA V native game events (damage, explosions, entity interactions).
@OnTick()Executes on every client tick. Avoid heavy computations to prevent FPS drops.
@Interval()Executes at a fixed time interval (ms). Prefer over OnTick when possible.
@Key()Binds the method to a keyboard key press.
@OnView()Registers a WebView callback handler (bridge between UI and gameplay logic).
@Export()Exposes the method as a FiveM client export.
@OnResourceStart()Runs when the resource starts.
@OnResourceStop()Runs when the resource stops.

Design Notes​

  • Server: Controllers are request-driven (commands, events).
  • Client: Controllers are event-driven (keys, ticks, WebView).
  • Prefer @Interval() over @OnTick() when possible to reduce CPU usage.
  • @LocalEvent() is the recommended way to communicate between client systems.
  • @OnGameEvent() is powerful but low-level — use it only when FiveM-native events are insufficient.