C++ Inherited template classes don't have access to the base class [duplicate]

问题

This question already has answers here:

“not declared in this scope” error with templates and inheritance [duplicate] (2 answers)

Closed 5 years ago.

I am working with template classes for the first time, and trying to figure out why the compiler doesn't seem to like when I use inheritence.

Here is the code:

template <typename T>
struct xPoint2
{
    T x;
    T y;

    xPoint2() { x = 0; y = 0; };
};

template <typename T>
struct xVector2 : xPoint2<T>
{
    xVector2() { x = 0; y = 0; };
};

The compiler output:

vector2.hh: In constructor ‘xVector2<T>::xVector2()’:
vector2.hh:11: error: ‘x’ was not declared in this scope
vector2.hh:11: error: ‘y’ was not declared in this scope

Is it not possible to use templates in this way?

Thanks

回答1:

You need to help the compiler out by using this->x and this->y.

http://www.parashift.com/c++-faq/templates.html#faq-35.19

回答2:

You must explicitly refer to parent:

template <typename T>
struct xVector2 : xPoint2<T>
{
    typedef xPoint2<T> B;
    xVector2() { B::x = 0; B::y = 0; };
};

来源：https://stackoverflow.com/questions/4810272/c-inherited-template-classes-dont-have-access-to-the-base-class