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Systems (the “S” in ECS) contain game logic that act on entities with the desired components. For example:
  • A physics system acts on all entities that have a mass and position component
  • A regen system acts on all entities that have a health component
  • A player movement system acts on all entities that have a position component

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Registering Systems

Before your systems can run, you need to register them with the world using cardinal.RegisterSystem(). 
func main() {
    world := cardinal.NewWorld()

    // Spawn player at tick 0 (only once)
    cardinal.RegisterSystem(world, system.PlayerSpawnerSystem, cardinal.WithHook(cardinal.Init))

    // Register player movement system (runs every tick)
    cardinal.RegisterSystem(world, system.PlayerMoveSystem)

    world.StartGame()
}
Systems can be registered with different hooks to control when they execute during the game loop.
HookWhen it runs
cardinal.WithHook(cardinal.Init)Once during world initialization (only once at tick 0), before any game loop starts
cardinal.WithHook(cardinal.PreUpdate)Every tick, before the main update phase
cardinal.WithHook(cardinal.Update)Every tick, during the main update phase (this is the default if no hook is specified)
cardinal.WithHook(cardinal.PostUpdate)Every tick, after the main update phase

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Next Steps

Before you start writing systems, there’s an important concept to learn: how to search for entities with components. Click next below to learn more.
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