For example, a camera that generates Raycast and if it hits it destorys an object.

public class RaycastScript : MonoBehaviour
{
    void CheckForRaycastHit()
    {
        RaycastHit hit;

        //if raycast hit 
        if(Physics.Raycast(transform.position, transform.forward, out hit))
        {
            print(hit.collider.gameObject.name + " hit");       //print what object got hit
            Destroy(hit.collider.gameObject);                   //destroy object
        }
    }
    void Update()
    {
        //mouse controls camera
        float mouseX = Input.GetAxis("Mouse X");
        float mouseY = Input.GetAxis("Mouse Y");

        transform.Rotate(-mouseY, 0, 0);
        transform.Rotate(0, mouseX, 0,Space.World);

        CheckForRaycastHit();
    }
}

Instead of destroying I want to disable mesh renderer so the object is invisible but still there.
I have been trying playing around with ".GetComponent()", looking in Unity documentation and some other things but I could not figure it out.

>Solution :

Get Mesh Renderer like bellow:

var meshRenderer = hit.collider.GetComponent<MeshRenderer>();

if (meshRenderer) meshRenderer.enabled = false;