How do I detect if object is geting hit by ray

Questions & Answers
1

So , I have a ray thats created evry time i click mouse button , and ray can detect what its hitting , but how do I detect of other objects side if its geting hit by the ray so I can take some health away

using UnityEngine;
using System.Collections;

public class shoot : MonoBehaviour {

Ray ray;

// Use this for initialization
void Start () {

}

// Update is called once per frame
void Update () {
	RaycastHit hit;

	if (Input.GetMouseButtonDown (0)) {
		if (Physics.Raycast (transform.position, transform.forward, out hit)) {
			Debug.Log (hit.transform.name);
			Debug.DrawRay (transform.position, transform.forward, Color.red, 25f);
		
		}
	}

}

}

2

Since you have the object hit saved in the Raycast hit variable, you can use the GetComponent function : Documentation for Get Component and then call a public function on the GameObject.

For example, imagine the script you have on the object you want to hit is named ActorEnemyManager which have a public function Damage(float amount), then you could do the following :

         if (Physics.Raycast (transform.position, transform.forward, out hit)) {
             Debug.Log (hit.transform.name);
             Debug.DrawRay (transform.position, transform.forward, Color.red, 25f);
         
             ActorEnemyManager actorEnemyManager = hit.transform.GetComponent<ActorEnemyManager>();
             if (actorEnemyManager != null) //  Checking if we found a component
                actorEnemyManager.Damage(10.0f);
         }
3

You could use use two classes. One sending the ray and one receiving the ray. When the ray hits the object use GetComponent to get a class attached to the recieving object and then call a public method to apply damage. Also in your question you said click. If you want to call the function on a click you should use Input.GetMouseButton and use Input.GetMouseButtonDown if you want to call it the method whenever the mouse button is being held down.
In the class sending the ray:

public float damage = 100f;

void Update(){
    if(Input.GetMouseButton(0))
        RayClick();
}

void RayClick (){
    RaycastHit hit = new RaycastHit;

    if (Physics.Raycast (transform.position, transform.forward, out hit)){
        ReceivingClass rc = hit.transform.GetComponent<ReceivingClass>();
    if(rc != null)
        rc.Damage(damage);
    }
}

Then in the class to receive the damage:

public float health = 500f;

public void Damage(float damageReceived){
    health -= damageReceived;

    if(health <= 0f)
        //Die...
}