c++ - 如何添加最终覆盖

Question

如何添加“最终覆盖”来解决这个问题？

#include <iostream>

struct Shape
{
  virtual void print()
  {
    std::cout << "SHAPE" << std::endl;
  }
  virtual ~Shape() {}
};

struct Box : public virtual Shape
{
  void print() 
  {
    std::cout << "BOX" << std::endl;
  }
};

struct Sphere : public virtual Shape
{
  void print() final override
  {
    std::cout << "SPHERE" << std::endl;
  }
};

struct GeoDisc : public Box, public Sphere
{
};

int main(int argc, char** argv)
{
  Shape* s = new GeoDisc;

  s->print();

  delete s;

  return 0;
}

这是错误信息:
31:8: 错误:'GeoDisc' 中的'virtual void Shape::print()' 没有唯一的最终覆盖

Answer 1

虚方法声明中的关键字 final 防止多重继承，所以如果我试图解决这种情况下的歧义，那是错误的方法。如果 Box 和 Sphere 都有 final word，你会得到错误“virtual function 'Shape::print' has more than one final overrider in 'GeoDisc'”。法律歧义解决方案是:

struct Sphere : public virtual Shape
{
  void print() override
  {
    std::cout << "SPHERE" << std::endl;
  }
};

struct GeoDisc : public Box, public Sphere
{
  void print() final override
  {
    Sphere::print();
  }
};