How to access a typedef of a template template class

Question

When trying to compile the following code:

class Object
{
};

template <class OBJECT>
class Manager
{
public:
    typedef OBJECT Object_t;
};

template <class MANAGER>
class Container
{
    MANAGER::Object_t m_obj;
};

Container<Manager<Object> > container;

I get the following error:

prog.cpp:15: error: type ‘MANAGER’ is not derived from type ‘Container’

prog.cpp:15: error: expected ‘;’ before ‘m_obj’

Thanks

possible duplicate of [Where and why do I have to put the "template" and "typename" keywords?](http://stackoverflow.com/questions/610245/where-and-why-do-i-have-to-put-the-template-and-typename-keywords) — Mike Seymour, Jul 02 '12 at 18:25

jxh · Answer 1 · 2012-07-02T18:49:02.947

You need typename since the compiler does not know that MANAGER::Object_t refers to a type when it is parsing the template.

typename MANAGER::Object_t m_obj;

The first error message means the compiler is treating the scoped MANAGER:: token as trying to access a base class member of Container. The second error message indicates the compiler didn't know that m_obj was supposed to be a data member, since it didn't recognize the token before it to be a type.

How to access a typedef of a template template class

1 Answers1