CODEWITHSUNDEEP
c++templatesoperator-overloading
Demion
Demion

Reputation: 877

template conversion operator

I want to overload conversion operator for two templates.

A.h

#pragma once

#include <B.h>

template <typename T> class A
{
operator B<T>() const;
}

B.h

#pragma once

#include <A.h>

template <typename T> class B
{
operator A<T>() const;
}

I got error

error C2833: 'operator A' is not a recognized operator or type see
reference to class template instantiation 'B<T>' being compiled

Although it works if conversion operator is overloaded only in one template.

Upvotes: 1

Views: 469

Answers (1)

Robert Mason
Robert Mason

Reputation: 4039

You have a cyclic dependency problem. You need to have a forward declaration, such as:

A.h:

#pragma once

template <class T> class B;

template <class T> class A {
   operator B<T>() const;
};

#include "B.h"

template <class T>
A<T>::operator B<T>() const {
   foo();
}

B.h:

#pragma once
#include "A.h"

template <class T>
class B {
   operator A<T>() const {
      bar();
   }
};

I assume you used #include "A.h". A.h then included B.h. When the compiler started compiling B.h, it had not yet seen a declaration for A.h, and thus the compiler did not know how to interpret operator A<T>() const, as it does not know that A is a type.

Upvotes: 2

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