The Rule of Five

The Rule of Five is an extension of the Rule of Three. While the Rule of Three states that if you define any of the destructor, copy constructor, or copy assignment operator, you should probably define all three, the Rule of Five adds two more special member functions to the list:

1. Move constructor
2. Move assignment operator

The Rule of Five is relevant in C++11 and later, where move semantics were introduced. Move semantics allow efficient transfer of resources from one object to another, avoiding unnecessary copying.

Here's an example of a class that follows the Rule of Five:

1class MyClass {
2public:
3  // Default constructor
4  MyClass() {}
5
6  // Destructor
7  ~MyClass() {}
8
9  // Copy constructor
10  MyClass(const MyClass& other) {}
11
12  // Copy assignment operator
13  MyClass& operator=(const MyClass& other) {}
14
15  // Move constructor
16  MyClass(MyClass&& other) {}
17
18  // Move assignment operator
19  MyClass& operator=(MyClass&& other) {}
20};

By defining all five special member functions, you have full control over how your objects are created, copied, moved, and destroyed. This is particularly important when your class manages resources like memory, file handles, or network connections.

The Rule of Five helps ensure that your class behaves correctly and efficiently in all situations, preventing resource leaks and unexpected behavior.