Question

下面是我的代码，总是在classD处提示错误 error C2504: 'C' : base class undefined

#include<iostream>
using namespace std;
class A{
public:
A(int a):x(a){cout<<"A constructor..."<<x<<endl;}
int f(){return ++x;}
~A(){cout<<"destructor A..."<<endl;}
private:
int x;
};

class B:public virtual A{
private:
int y;
A Aobj;
public:
B(int a,int b,int c):A(a),y(c),Aobj(c){cout<<"B constructor..."<<y<<endl;}
int f(){
A::f();
Aobj.f();
return ++y;
}
void display(){cout<<A::f()<<"\t"<<Aobj.f()<<"\t"<<f()<<endl;}
~B(){cout<<"destructor B..."<<endl;}
};

class C:public B{
public:
C(int a,int b,int c):B(a,b,c),A(0){cout<<"C constructor..."<<endl;
};

class D:public C,public virtual A{
public:
D(int a,int b,int c):C(a,b,c),A(c){cout<<"D constructor..."<<endl;}
~D(){cout<<"destructor D..."<<endl;}
};
void main(){
D d(7,8,9);
d.f();
d.display();
}

Answer 1

C(int a,int b,int c):B(a,b,c),A(0){cout<<"C constructor..."<<endl;//少了}