break Protected member access解决方法

#include "stdafx.h"


// Library code
template<class DerivedT>
class Base
{
private:
    struct accessor : DerivedT    //DerivedT是派生类,其中成员函数do_foo是个保护函数
    {
        static int foo(DerivedT& derived)
        {
            int (DerivedT::*fn)() = &accessor::do_foo;    //获得父类do_foo的函数地址？？？？？ 
            return (derived.*fn)();   //获得地址后，然后用derived这个对象来调用
        }
    };


public:
    DerivedT& derived() {
        return static_cast<DerivedT&>(*this); }
    int foo()
    {
        return accessor::foo(derived()); 
    }
};