Ray from a cube to a touch point to help aiming

Hello,

I want to achieve this: there is cube and from that cube must come out a visible Ray to the point of the screen where the player touches the screen with the finger. The visible Ray is not an Arch must be a straight line therefore there is no calculation of the trajectory involved.

This is for an iOS game and for the vector I use Vectrosity, However vectrosity does not seem the problem I think Is how I pass the variable to. The code compiles with no mistakes but with warning which are: Line 7 "vectorLIne is never assigned to and will always be null" but I believe it is assigned. Line 15 "The variable vectorLine is assigned but it's value is never used " which is the opposite of what says in line 7.! Line 28 " the variable touchPos is assigned but it value never used.. That is true but is the only way I can put the values inside the vectorLine.Points Can someone tell me where is my mistake?

 sing UnityEngine;
 using System.Collections;
 using Vectrosity;
 
 public class NewBehaviourScript1 : MonoBehaviour {
 
     VectorLine vectorLine;
     Material material = null;
 
 
     // Use this for initialization
     void Start ()
     {
         var linePoints = new Vector2[2];
         var vectorLine = new VectorLine("Myline", linePoints, material, 2.0f);
     
     }
     
     // Update is called once per frame
     void Update () {
 
         int fingerCount = 0;
         foreach (Touch touch in Input.touches) {
             if (touch.phase != TouchPhase.Ended && touch.phase != TouchPhase.Canceled)
                 fingerCount++;
             if (fingerCount > 0){
                 Vector3 worldPoint = Camera.main.ScreenToWorldPoint(touch.position);
                 Vector2 touchPos = new Vector2(worldPoint .x, worldPoint.y);
                 vectorLine.points2[0] = new Vector2(worldPoint.x,worldPoint.y);
                 vectorLine.points2[1] = new Vector2(worldPoint.y, worldPoint.x);
                 vectorLine.Draw();
 
 
             }
         }
 
     }
 }

I am stuck with this problem for more than 2 weeks. Any help will be appreciated.

Thanks

CL