c++ - 两个类如何能够相互使用？

Question

比如这种情况

class Node {
public:
    int index;
    std::vector<Edge> outs;
};

class Edge {
public:
    double weight;
    Node vertex;
};

Answer 1

Let me make a statement first.

#include<vector>

class Edge;

class Node {
public:
    int index;
    std::vector<Edge> outs;
};

class Edge {
public:
    double weight;
    Node vertex;
};

Strictly speaking, Node should use Edge pointers or references, or explicitly support incomplete type containers. However, generally vectors are implemented based on pointers, so there is no problem.

Answer 2

Calling classes to each other feels like there is something wrong with this design