如下代码:#include #include using namespace std;class Music {public: Music(const string& str):name(str) {} string name;};class Person {public: void listen(Music & music = Music("我的祖国")) { play(music); } void listen(const Music & music = string("我的祖国")) { play(music); } void listen(Music * music = nullptr) { if(music == nullptr) music = new Music("我的祖国"); play(*music); } void listen(const Music * music = new Music("