C++ — 前置声明

类的前置声明

class Parent;  //前置声明

class Child {
public:
    explicit Child(Parent* p) : m_parent(p) {}
private:
    Parent* m_parent;
};

class Parent {
public:
    bool addChild(Child* child) { m_children.push_back(child); }
private:
    std::vector<Child* >m_children;
};