详解C++成员函数的override和final说明符的用法

function-declaration override;

class BaseClass
{
  virtual void funcA();
  virtual void funcB() const;
  virtual void funcC(int = 0);
  void funcD();
};

class DerivedClass: public BaseClass
{
  virtual void funcA(); // ok, works as intended

  virtual void funcB(); // DerivedClass::funcB() is non-const, so it does not
             // override BaseClass::funcB() const and it is a new member function

  virtual void funcC(double = 0.0); // DerivedClass::funcC(double) has a different
                   // parameter type than BaseClass::funcC(int), so
                   // DerivedClass::funcC(double) is a new member function

};

class BaseClass
{
  virtual void funcA();
  virtual void funcB() const;
  virtual void funcC(int = 0);
  void funcD();
};

class DerivedClass: public BaseClass
{
  virtual void funcA() override; // ok

  virtual void funcB() override; // compiler error: DerivedClass::funcB() does not 
                  // override BaseClass::funcB() const

  virtual void funcC( double = 0.0 ) override; // compiler error: 
                         // DerivedClass::funcC(double) does not 
                         // override BaseClass::funcC(int)

  void funcD() override; // compiler error: DerivedClass::funcD() does not 
              // override the non-virtual BaseClass::funcD()
};

function-declaration final;

class class-name final base-classes

class BaseClass
{
  virtual void func() final;
};

class DerivedClass: public BaseClass
{
  virtual void func(); // compiler error: attempting to 
             // override a final function
};

class BaseClass final 
{
};

class DerivedClass: public BaseClass // compiler error: BaseClass is 
                   // marked as non-inheritable
{
};