CODEWITHSUNDEEP
c++c++11templatesc++14generic-programming
Cherkesgiller
Cherkesgiller

Reputation: 520

Cannot access type alias from class template definition in separate file without typing full declaration of alias type

I have a class template like Sample.hpp with type alias X.

#ifndef SAMPLE_HPP
#define SAMPLE_HPP

template<typename STA, typename STB>
class Sample
{
    using X = Sample<STA,STB>;

public:
    Sample();
    inline X* GetNext() const;

private:
    X* Next;
};

#include "Sample.cpp"

#endif // SAMPLE_HPP

And definitions are in Sample.cpp. 

#include "Sample.hpp"

template<typename STA, typename STB>
Sample<STA,STB>::Sample() {
    Next = nullptr;
}

template<typename STA, typename STB>
typename Sample<STA,STB>::X* Sample<STA,STB>::GetNext() const {
    return this->Next;
}

My question is that, are there any others ways of defining GetNext function. For example without typename or without full declaration of Sample class template. When I change code to

template<typename STA, typename STB>
Sample<STA,STB>* Sample<STA,STB>::GetNext() const {
    return this->Next;
}

It works, but I cant use type alias here directly , for example : 

template<typename STA, typename STB>
X* Sample<STA,STB>::GetNext() const {
    return this->Next;
}

Upvotes: 1

Views: 465

Answers (1)

Rakete1111
Rakete1111

Reputation: 48938

You can use a trailing return type with the help of auto:

template<typename STA, typename STB>
auto Sample<STA, STB>::GetNext() const -> X* {
    return this->Next;
}

Upvotes: 5

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