C++中虚继承时的构造函数示例详解

    #include <iostream>
    using namespace std;
    //虚基类A
    class A{
    public:
        A(int a);
    protected:
        int m_a;
    };
    A::A(int a): m_a(a){ }
    //直接派生类B
    class B: virtual public A{
    public:
        B(int a, int b);
    public:
        void display();
    protected:
        int m_b;
    };
    B::B(int a, int b): A(a), m_b(b){ }
    void B::display(){
        cout<<"m_a="<<m_a<<", m_b="<<m_b<<endl;
    }
    //直接派生类C
    class C: virtual public A{
    public:
        C(int a, int c);
    public:
        void display();
    protected:
        int m_c;
    };
    C::C(int a, int c): A(a), m_c(c){ }
    void C::display(){
        cout<<"m_a="<<m_a<<", m_c="<<m_c<<endl;
    }
    //间接派生类D
    class D: public B, public C{
    public:
        D(int a, int b, int c, int d);
    public:
        void display();
    private:
        int m_d;
    };
    D::D(int a, int b, int c, int d): A(a), B(90, b), C(100, c), m_d(d){ }
    void D::display(){
        cout<<"m_a="<<m_a<<", m_b="<<m_b<<", m_c="<<m_c<<", m_d="<<m_d<<endl;
    }
    int main(){
        B b(10, 20);
        b.display();
        C c(30, 40);
        c.display();
        D d(50, 60, 70, 80);
        d.display();
        return 0;
    }

D::D(int a, int b, int c, int d): B(90, b), C(100, c), A(a), m_d(d){ }