Usually you'd have the "physics" system hold onto the array while the EntityData would hold a pointer to the PhysicsComponent for that Entity. That way each en

Usually you'd have the "physics" system hold onto the array while the EntityData would hold a pointer to the PhysicsComponent for that Entity. That way each entity can access it's data quickly, and if there is some heavy physics computation it can easily iterate it in a list (aka checking for collisions).