if a gameobject in clicked code example

Example 1: unity know when gameobject presed

void Update () {
         if (Input.GetMouseButtonDown(0)) {
             CastRay();
         }       
     }

     void CastRay() {
         Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
         RaycastHit2D hit = Physics2D.Raycast (ray.origin, ray.direction, Mathf.Infinity);
         if (hit.collider !=null) {
             Debug.Log (hit.collider.gameObject.name);
     }

Example 2: unity if gameobject is clicked

void OnMouseDown() 
 {
   Debug.Log("Mouse is down")
 } 

 void OnMouseUp() 
 {
   Debug.Log("Mouse is up")
 } 

 void OnMouseClick() 
 {
   Debug.Log("Mouse is clicked (down then up its 1 click)")
 } 

// Works only if the gameobject have a collider