我重写此方法的方式有什么问题？

Question

I'm trying to build a ray tracer. I have a class called Shape which I'm extending to the class of Sphere (and other shapes as well, like triangles). Shape has the method

virtual bool intersect(Ray) =0;

And so I create the Sphere class by

class Sphere : public Shape{
public:
    Sphere(){};
    bool intersect(Ray){/*code*/};
};

I have a main class which I use to create a list of Shape pointers. I create a Sphere pointer and do the following:

Sphere* sph = &Sphere();
shapes.emplace_front(sph); //shapes is a list of Shape pointers

Then when I want to trace the ray in another class I do the following:

for (std::list<Shape*>::iterator iter=shapes.begin(); iter != shapes.end(); ++iter) {
    Shape* s = *iter;
    bool hit = (*s).intersect(ray);
}

But I get the error that I cannot call intersect on a the virtual class Shape, even though it should be that *s points to a Sphere type object. What am I doing wrong with inheritance?

Answer 1

One problem is this:

Sphere *sph = &Sphere();

It creates a temporary object of type Sphere , stores a pointer to that temporary, then destroys the temporary. The result is nonsense.

Change it to this:

Sphere *sph = new Sphere();

things will work much better.