为什么我不能访问静态多态派生类中的受保护成员？

Question

This works fine:

    class A{
    protected:
    int i;
    };

    class B:public A{
    public:
    void f(){
        i=5; //fine
      }
    };

However if I try to do the same with static polymorphism, it fails:

template <class Derived, typename T, int N>
class Vector{

protected:

std::vector<T> v;

Then:

  template <typename T, int N>
  class Vector234:public Vector<Vector234<T, N>,T,N>{

    void test(){
        T t=v[0]; // v is undeclared identifier
    }

Why is this?

Answer 1

Because it's a dependent name, that is, it depends on the template parameter T . You need to explicitly specify either this->v[0] or Vector<Vector234<T, N>,T,N>::v[0] .