Behavior Class

Definition

Namespace: Brine2D.ECS

Base class for behaviors, which contain logic that operates on a single entity. Each entity gets its own behavior instance with constructor injection support.

public abstract class Behavior

Inheritance System.Object → Behavior

Remarks

Use behaviors for entity-specific logic (player movement, boss AI, etc.). For batch processing of many entities, use systems instead.

Ambient vs. parameter-passed:Behavior exposes its framework services (Entity, Input, Renderer, Logger, Audio, Game) as ambient properties, the same convention Scene/SceneBase use, because exactly one behavior instance is bound to exactly one entity for its entire attached lifetime, so the context never changes between OnAdded(), Update\(GameTime\), FixedUpdate\(GameTime\), Render\(IRenderer, GameTime\), and any other lifecycle callback, so there is no need to re-supply it on every call. Systems (IUpdateSystem, IFixedUpdateSystem, IRenderSystem) are the opposite shape: a single system instance batch-processes many entities per call, so there is no single "current entity" to be ambient about. Those APIs instead take the IEntityWorld (and entities/components within it) as explicit parameters. Prefer ambient properties for anything scoped to "this behavior's entity, for as long as it's attached"; prefer parameters for anything that varies per call or per entity within a single call.

Execution order: During Brine2D.ECS.EntityWorld.Update\(Brine2D\.Core\.GameTime\), all IUpdateSystems run first (sorted by UpdateOrder), then all behaviors (sorted by UpdateOrder). During Brine2D.ECS.EntityWorld.FixedUpdate\(Brine2D\.Core\.GameTime\), all IFixedUpdateSystems run first (sorted by FixedUpdateOrder), then all behaviors (sorted by FixedUpdateOrder). During Brine2D.ECS.EntityWorld.Render\(Brine2D\.Rendering\.IRenderer,Brine2D\.Core\.GameTime\), all IRenderSystems run first (sorted by RenderOrder), then all behaviors (sorted by RenderOrder). Behaviors therefore always execute after system-rendered content. If you need to render between systems, move the render logic into a custom IRenderSystem with the appropriate RenderOrder.

public class PlayerMovementBehavior : Behavior
{
    public override int UpdateOrder => 10;

    public override void Update(GameTime gameTime)
    {
        if (Input.IsKeyDown(Key.W))
            Audio.PlaySound(_footstep);
    }
}