C++ returning protected struct pointer in template class

Question

Please help me I don't know what happens. It shows error C2955: 'MyClass' : use of class template requires template argument list

template <class T> class MyClass
{
protected:
    struct MyStruct
    {
    };

    MyStruct* GetElement(...) const;
}

//error C2955: 'MyClass' : use of class template requires template argument list
//I tried: 
// MyClass<T>::MyStruct* MyClass<T>::GetElement(...) const
// MyStruct* MyClass<T>::GetElement(...) const
// but none works. This method doesn't use T.
template<class T>
MyClass::MyStruct* MyClass<T>::GetElement(...) const
{

}

πάντα ῥεῖ · Accepted Answer · 2014-07-15 16:30:34Z

1

These fixes work

template <class T> class MyClass {
protected:
    struct MyStruct
    {
    };

    MyStruct* GetElement(...) const;
}; // << add semicolon

template <class T>
// Add typename
typename MyClass<T>::MyStruct* MyClass<T>::GetElement(...) const {
     // Add <T> ^^^
    return NULL;
}

Any type that depends on the template parameter must be specified with typename.

edited Jul 15, 2014 at 16:30

answered Jul 15, 2014 at 16:21

πάντα ῥεῖ

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Comments

Community · Accepted Answer · 2017-05-23 11:57:51Z

0

The return type of GetElement should be written as typename MyClass<T>::MyStruct*:

template<class T>
typename MyClass<T>::MyStruct* MyClass<T>::GetElement(...) const
{

}

The <T> is necessary because MyClass is a template class. typename is needed because MyClass<T>::MyStruct is a dependent name.

edited May 23, 2017 at 11:57

CommunityBot

11 silver badge

answered Jul 15, 2014 at 16:21

user2555451

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