string a = "1";
   string b = a;
   a = "2";
   print(b);
  
   GameObject a = new GameObject("1");//game object 有一个 name 构造
   GameObject b = a;
   a.name = "2";
   print(b.name);
 
   Vector2 a = new Vector2(1, 1);
   Vector2 b = a;
   a.x = 2;
   print(b.x);
 
   GameObject a = new GameObject("1");
   GameObject b = a;
   a = new GameObject("2");
   print(b.name);