raycast activation by trigger

Hi, there's a code which allow the player casting a raycast because i have plenty's of object that will react by being touches by a ray.

 public float activeDist;
 public GameObject raycast;

 void Start () {

     raycast.SetActive (false);
 }



 void Update () {

     RaycastHit hit;

     if (Cardboard.SDK.Triggered) {

         raycast.SetActive (true); 
         Ray casting = new Ray (transform.position, Vector3.forward);
     
         Debug.DrawRay (transform.position, Vector3.forward * activeDist); 

         ----> raycast.SetActive (false); <--------------------
     }

So then i run the game if i trigger the button, it cast a ray forever so it isn't juste when i push the button and if i use the last line ("raycast.SetActive(false);") i doesn't work at all ! My other objects don't detect that a ray is touching them.