通過傳址來傳遞和返回對象

#include <iostream>
using namespace std;
class c{
public:
    void set(int n) {num=n;}
     int get() const {return num;}
private:
      int num;
};
void f(c&);
C& g();
int main()
{
    C c1,c2;
    f(c1);
    c2=g();
    cout<<c2.get()<<'\n';
    return 0;
}
void f(c& c)
{
    c.set(-999);
    cout<<c.get()<<'\n';
}
C& g()
{
   static C c3;
   c3.set(123);
   return c3;
}