Nested class of a template class, static member variable of the template class

Question

The following code works:

template<typename T> class OtherClass
{
public:
    T member;
};

template<typename T> class MyClass
{         
public:
    vector<vector<OtherClass<T> > * > stacks;
};

template<typename T>
static vector<vector<OtherClass<T> > * > MyClass<T>::stacks =
    vector<vector<OtherClass<T> > * >(1024);

But this one does not:

template<typename T> class MyClass
{         
public:
    class OtherClass
    {
    public:
        T member;
    };

    static vector<vector<OtherClass> * > stacks;
};

template<typename T>
vector<vector<MyClass<T>::OtherClass> * > MyClass<T>::stacks =
    vector<vector<MyClass<T>::OtherClass> * >(1024);

gcc complains amongst other things: error: type/value mismatch at argument 1 in template parameter list for 'template class vector'

Any idea how to nest the class?

Thanks!

galop1n · Accepted Answer · 2014-02-04 18:52:37Z

3

you need to tell the compiler that OtherClass is a nested type with typename

template<typename T>
vector<vector<typename MyClass<T>::OtherClass> * > MyClass<T>::stacks =
    vector<vector<MyClass<T>::OtherClass> * >(1024);

And no need to repeat the type twice :

template<typename T>
vector<vector<typename MyClass<T>::OtherClass> * > MyClass<T>::stacks (1024);

If you do not wants to repeat a complex original type, use typedef, still needing typename :

// in Myclass : using StackType = vector<vector<OtherClass>*>;
template<typename T>
typename MyClass<T>::StackType MyClass<T>::stacks (1024);

edited Feb 4, 2014 at 18:52

answered Feb 4, 2014 at 18:35

galop1n

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