Where to store reference to objects?

I have a

ComponentSystem

that wants to perform raycast from camera.
I don't want to use Camera.main inside

OnUpdate

. I want to cache the camera somewhere and use that.
So what's the best way to do it? Should I use

SystemStateComponent

?

 

Code (CSharp):

1.  public class MyCameraSystem : ComponentSystem
2.     {
3.       Camera camera;
4.         protected override void OnCreateManager()
5.         {
6.             camera = Camera.main; // reference here
7.         }
8.      
9.  
10.         protected override void OnUpdate( )
11.         {
12.           // use camera here
13.          }
14.    }