Question

I have created a template class(TBase) that defines another class(BaseUDT) within its body.

#pragma once

template<class T>
class TBase
{
public:
    class BaseUDT
    {
    public:
        int a;
    };
    T m_base;
};

Now, i create a class(TDerived) that derives from TBase.

template<class T>
class TDerived : public TBase<T>
{
public:
    T m_derived;
    BaseUDT m_baseUDT;
};

This code compiles on Visual Studio but when I try compiling it on Xcode on a Mac machine, it throw compile errors. Using TBase::BaseUDT doesn’t work either.

I have been trying to go through the ISO c++ docs but still haven’t found anything relevant so far.

Answer 1

Its name is dependent – declare it like so:

template<class T>
class TDerived : public TBase<T>
{
public:
  T m_derived;
  typename TBase<T>::BaseUDT m_baseUDT;
};