supertrait.h

/*
    SPDX-FileCopyrightText: 2009 Volker Krause <vkrause@kde.org>
 
    SPDX-License-Identifier: LGPL-2.0-or-later
*/
 
#pragma once
 
namespace Akonadi
{
namespace Internal
{
template<typename T>
struct check_type {
    using type = void;
};
}
 
/**
  @internal
  @see SuperClass
*/
template<typename Super, typename = void>
struct SuperClassTrait {
    using Type = Super;
};
 
template<typename Class>
struct SuperClassTrait<Class, typename Internal::check_type<typename Class::SuperClass>::type> {
    using Type = typename Class::SuperClass;
};
 
/**
  Type trait to provide information about a base class for a given class.
  Used eg. for the Akonadi payload mechanism.
 
  To provide base class introspection for own types, extend this trait as follows:
  @code
  namespace Akonadi
  {
    template <> struct SuperClass<MyClass> : public SuperClassTrait<MyBaseClass>{};
  }
  @endcode
 
  Alternatively, define a typedef "SuperClass" in your type, pointing to the base class.
  This avoids having to include this header file if that's inconvenient from a dependency
  point of view.
*/
template<typename Class>
struct SuperClass : public SuperClassTrait<Class> {
};
}