When to use " new " and when not to, in C++?

In C++, the new keyword is used for dynamic memory allocation, which allocates memory on the heap for objects or arrays and returns a pointer to the allocated object. Every instance created with new should be deallocated using delete to prevent memory leaks. Whether to use new depends on several factors. Below are some guidelines:

When to Use new

1. Long-term storage requirements: When you need to retain data across multiple parts of the program, where the lifetime of the data exceeds its creation scope, using new is appropriate. For example, you might create an object within a function and want it to remain available after the function returns.

   Example:

   cpp
   MyClass* myObject = new MyClass();

2. Large objects or arrays: For very large objects or arrays, dynamic memory allocation helps prevent stack overflow, as the stack (for static or automatic allocation) typically has size constraints.

   Example:

   cpp
   int* bigArray = new int[1000000];

3. Control over object creation and destruction: Using new enables precise control over the timing of object creation and destruction.

   Example:

   cpp
   MyClass* myObject = new MyClass();
   // After usage, delete myObject;

When Not to Use new

1. Local objects: When an object is used only within a single function or scope, stack allocation (i.e., automatic variables) is preferable. This approach is simple and does not require manual memory management.

   Example:

   cpp
   MyClass myObject;

2. Smart pointers: In modern C++, it is recommended to use smart pointers (such as std::unique_ptr, std::shared_ptr) to manage dynamic memory, as they automatically release resources, reducing the risk of memory leaks.

   Example:

   cpp
   std::unique_ptr<MyClass> myObject = std::make_unique<MyClass>();

3. Standard containers: For arrays and similar collection data structures, standard containers (such as std::vector, std::map, etc.) are safer and more efficient, as they manage memory automatically.

   Example:

   cpp
   std::vector<int> myArray;
   myArray.push_back(10);

In summary, using new in C++ is necessary but must be handled carefully to avoid memory leaks. In modern C++ practices, it is recommended to use smart pointers and standard containers as much as possible to simplify memory management.