类及其成员的继承和多态性(shared_ptr，C++11）

我正在处理以下使用std:：shared_ptr(C++11(的类结构：

#include <string>
#include <iostream>
#include <vector>
#include <memory>
//class Member is given by a 3rd party library, CAN'T modify its structure!
class Member {//no instance of this class allowed
   public:
     Member() {};//should never be called
     virtual ~Member() = 0;//pure virtual distructor;
     virtual void foo() {
       std::cout<<"Member"<<std::endl;
     }
};
Member::~Member() {} //need to define destructor because of child classes 
class ChildMember : public Member {
  public:
     ChildMember() {};
     virtual void foo() {
         std::cout<<"Child Member"<<std::endl;
     }
     virtual void foo2() {
        std::cout<<"unique foo in child"<<std::endl;
     }
};
class Base {
   public:
     Base() {};
   virtual
   std::shared_ptr< Member >
   get_var() {return var;}
   virtual void 
   set_var ( std::shared_ptr< Member > v) { var = v;}
   std::shared_ptr< Member > var;
};

class ChildBase : public Base {
  public:
     ChildBase() {
        //var = std::make_shared<ChildMember>();
     };
  virtual
  std::shared_ptr< ChildMember >
  get_var() {return var;} //(2) : try to comment
  virtual void 
  set_var ( std::shared_ptr< ChildMember > v) { var = v;}
  std::shared_ptr< ChildMember > var;
};
void func(std::shared_ptr<Base> b) {
    b->get_var()->foo();// process input using polymorphism
}
int main() 
{
    std::shared_ptr<ChildBase> cb( std::make_shared<ChildBase>());
    cb->set_var (std::make_shared<ChildMember>() );
    cb->get_var()->foo2();//(3) want to use unique functions of ChildBase;
    cb->var->foo2();      //can access directly as well;
    //cb->var = std::make_shared<ChildMember>();
    func(cb);
}

我尝试设计两个类(Base和ChildBase(，其中每个类都有自己的成员Member/ChildMember。在完全使用ChildBase对象及其类型为ChildMember的成员对象后，我将其传递给接收Base的函数func，并且应该使用多态性调用成员var的适当foo。

问题：(1(在上面的变体中，编译器抱怨道：

 overriding 'virtual std::shared_ptr<Member> Base::get_var()'
     get_var() {return var;}`

(2(如果我注释掉get_var的ChildBase实现，则此函数被视为Base，并因此返回指向没有foo2的Member的指针。

(3(我也可以评论cb->get_var()->foo2()。所有的东西都编译了，但似乎没有调用ChildMember::foo()，因为没有输出Child Member；

有些事情(希望(有点乱，但我不知道是什么。你们能帮忙纠正一下吗？

EDIT1：

基于Abhijit Kadam的回答，以下代码完全编译：

#include <string>
#include <iostream>
#include <vector>
#include <memory>
class Member {//no instance of this class allowed
   public:
     Member() {};
     virtual ~Member() = 0;//pure virtual distructor;
     virtual void foo() {
       std::cout<<"Member"<<std::endl;
     }
};
Member::~Member() {} //need to define destructor for child classes 
class ChildMember : public Member {
  public:
     ChildMember() {};
     virtual void foo() {
        std::cout<<"Child Member"<<std::endl;
     }
     void foo2() {
        std::cout<<"unique foo in child"<<std::endl;
     }
};
class Base {
   public:
     Base() {};
     std::shared_ptr< Member >
     get_var() {return var;}
     void set_var ( std::shared_ptr< Member > v) { var = v;}
     std::shared_ptr< Member > var;
};

class ChildBase : public Base {
  public:
     ChildBase() {
       //var = std::make_shared<ChildMember>();
     };  
     std::shared_ptr< ChildMember > var;
};
void func(std::shared_ptr<Base> b) {
    b->get_var()->foo();// process input using polymorphism
}
 void func_vec( std::vector< 
              std::shared_ptr<Base>
           > vec) {
     for (unsigned int i=0;i<vec.size();i++)
          vec[i]->get_var()->foo();
  }
int main() 
{
   std::shared_ptr<ChildBase> cb( std::make_shared<ChildBase>());
   cb->set_var (std::make_shared<ChildMember>() );
   func(cb);
   std::vector< std::shared_ptr<Base>> vec;
   vec.push_back(cb);
   func_vec(vec);
   cb->var->foo2();
   /*std::shared_ptr<ChildMember> ptr(std::dynamic_pointer_cast<ChildMember>(cb->get_var()) );
   if (ptr) {
      ptr->foo2();
   } */
}

编辑2在下面添加了一个答案。