1.1.9.4 When to use new

• When you use smart pointer. Here I change it to another question, When you use new
  1. An new object remain in existence, until you delete it. (you control the life time of it, maybe you create it in fun1,then delete it in fun4. so the obj is neither stack life nor global life. You may or may not transfer ownership between functions.)
  2. When you want to dynamic create a obj in runtime according runtime condition or user input. (maybe don’t create it. ) Below code demonstrate previous two conditions. ToothBrush need to be control life time and created dynamically.
     class Person{ 
     ToothBrush* pbrush; 
      
     buyNewBrush(string &name){ 
         if(pbrush != nullptr}{ 
                     delete pbrush; 
         } 
         if(name == "Orlab") 
               pbrush = new Brush(); 
         } 
     } 
     ~Person(){ 
             if(pbrush != nullptr}{ 
                     delete pbrush; 
         } 
     } 
     /////////////////// 
     Person Yan(); 
     Yan.buyNewBrush("Oralb"); 
     ......Three months later........... 
     Yan.buyNewBrush("Philip"); 
     }
  3. Large array or resources, if you allocate in stack, it will cause stack overflow.