c – 在模板化嵌套和继承类中未检测到的变量

template <typename U,typename T,typename _Prd = equal_to<T> >
class Octree
{
...
private :
    BBox<T,3,_Prd> bounds ;

    void SplitNode() ;
    virtual bool isSplit () ;
...
};


template <typename U,typename _Prd = equal_to<T> >
class Hull
{
    ...
    //nest the octree class here

    class OcHull: public Octree<U,T,_Prd>
    {
        bool isSplit () ;  
    };

    OcHull * GetOcHull() const ;

private:

    OcHull * hullstructure ;

};

当我想访问OcHull中的bounds变量时,编译器看不到它有这个变量.

template <typename U,typename _Prd>
bool Hull<U,_Prd>::OcHull::isSplit()
{
    assert(typeid(double) == typeid(T)) ;
    // for each possible view of currect cell

    for (size_t i = 0 ; i < camera_array.size() ; ++i)
    {
        //project centre of the cell

        // bounds is not detected. bound is meant to be inherited from BBox<T,_Prd> bounds ; above

        Vec<double,2> projectedP = camera_array[i].projectToCamPlane(bounds.centre) ; 

        ...


    }
}

错误是

Hull.hpp:84: error: ‘bounds’ was not declared in this scope

你能告诉我为什么它没有看到界限吗？