C++ Rule of Three

Rule of Three

The rule of three (also known as the Law of The Big Three or The Big Three) is a rule of thumb in C++ (prior to C++11) that claims that if a class defines one (or more) of the following it should probably explicitly define all three:^[1] 

• destructor
• copy constructor
• copy assignment operator

如果需要析构函数，则一定需要拷贝构造函数和赋值操作符