protected override void OnCreateManager()
        {
            base.OnCreateManager();

            commandCallbackSystem              = World.GetExistingManager <CommandCallbackSystem>();
            componentCallbackSystem            = World.GetExistingManager <ComponentCallbackSystem>();
            componentConstraintsCallbackSystem = World.GetExistingManager <ComponentConstraintsCallbackSystem>();
        }
        protected override void OnCreate()
        {
            base.OnCreate();

            commandCallbackSystem              = World.GetExistingSystem <CommandCallbackSystem>();
            componentCallbackSystem            = World.GetExistingSystem <ComponentCallbackSystem>();
            componentConstraintsCallbackSystem = World.GetExistingSystem <ComponentConstraintsCallbackSystem>();
            workerFlagCallbackSystem           = World.GetExistingSystem <WorkerFlagCallbackSystem>();
        }