QObject的多重继承

Question

I want to inherit QObject and another class and got an error: undefined reference for `vtable for EduGraph' I've read some threads about it and have fixed the sequence of the inherited classes in the class definition, but it haven't solved the problem.

class EduGraph : public QObject, public Graph<Vertex<ENode, EEdge>*> {
private:
    std::list<Vertex<ENode, EEdge>*>::iterator firstSel;
    std::list<Vertex<ENode, EEdge>*>::iterator secSel;
public:

Q_OBJECT

    EduGraph() : firstSel(0), secSel(0) {}
    ~EduGraph();

    void NewNode(const QPoint& p);
    void RemoveNode();
    void Associate();
    void Dissociate();

signals:
    void VertexSelected();
    void VertexDeSelected();
};

Answer 1

`Undefined reference to `vtable for...'` 

is usually a sign of unimplemented virtual function. Make sure you have implemented (defined) the corresponding virtual functions you inherited from the base classes .

For example this will give you the same error because the print method in B is not implemented.

class A {
public:
    virtual void print() = 0;
};

class B : public A{
public:
    void print();
};

int main()
{
    B b;
}