Add way to access scene object from within Actions

scene/scene.go

@@ -11,6 +11,24 @@ type Scene struct {
 	actions []Action
 }
 
+type sceneKey struct{}
+
+func InjectContext(ctx context.Context, s *Scene) context.Context {
+	return context.WithValue(ctx, sceneKey{}, s)
+}
+
+func FromContext(ctx context.Context) *Scene {
+	v := ctx.Value(sceneKey{})
+	if v == nil {
+		return nil
+	}
+	s, ok := v.(*Scene)
+	if !ok {
+		return nil
+	}
+	return s
+}
+
 func New() *Scene {
 	return &Scene{}
 }
@@ -21,6 +39,8 @@ func (s *Scene) Add(a Action) *Scene {
 }
 
 func (s *Scene) Execute(ctx context.Context) error {
+	ctx = InjectContext(ctx, s)
+
 	for _, a := range s.actions {
 		if err := a.Execute(ctx); err != nil {
 			return err