Line data    Source code

       1           0 : // Distributed under the MIT License.
       2             : // See LICENSE.txt for details.
       3             : 
       4             : #pragma once
       5             : 
       6             : #include "Utilities/TMPL.hpp"
       7             : 
       8             : /// \ingroup UtilitiesGroup
       9             : /// \brief Helpers for derived class registration
      10             : ///
      11             : /// SpECTRE's factory mechanism requires that the base class contain a
      12             : /// list of all derived classes (in the special nested type alias
      13             : /// `creatable_classes`).  This can be problematic when the desired
      14             : /// list of derived classes can vary with use of the base class.
      15             : /// These helpers provide a method to simplify handling these
      16             : /// compile-time registrations.
      17             : ///
      18             : /// Each optional derived class defines a registrar helper and both
      19             : /// the base class and derived classes are templated on the list of
      20             : /// registrars.  The typical structure of these classes is:
      21             : /// \snippet Test_Registration.cpp registrar_structure
      22             : /// A concrete base class type with a specific set of derived classes
      23             : /// is constructed like
      24             : /// \snippet Test_Registration.cpp registrar_use
      25             : ///
      26             : /// It is frequently useful to default the registrar list in a derived
      27             : /// class to the registrar for that class.  This ensures that any
      28             : /// methods in the base class using the registrar list (such as those
      29             : /// using `call_with_dynamic_type()`) work
      30             : /// as expected on an explicitly constructed derived class with the
      31             : /// list omitted.
      32           1 : namespace Registration {
      33             : /// A template for defining a registrar.
      34             : ///
      35             : /// A registrar for a class can be defined by making a type alias to
      36             : /// this struct, filling in the registrant.
      37             : /// \snippet Test_Registration.cpp registrar
      38             : /// In more complex cases (such as with non-type template
      39             : /// parameters) defining a registrar manually may be necessary.
      40             : /// \snippet Test_Registration.cpp custom_registrar
      41             : template <template <typename...> class Registrant, typename... Args>
      42           1 : struct Registrar {
      43             :   // Final registrant type, specialized with input Args... and the
      44             :   // RegistrarList it was extracted from.  This will be a full
      45             :   // specialization of a derived class that uses the registration
      46             :   // framework.
      47             :   template <typename RegistrarList>
      48           0 :   using f = Registrant<Args..., RegistrarList>;
      49             : };
      50             : 
      51             : namespace detail {
      52             : template <typename RegistrarList, typename Registrar>
      53             : struct registrant {
      54             :   using type = typename Registrar::template f<RegistrarList>;
      55             : };
      56             : }  // namespace detail
      57             : 
      58             : /// Transform a list of registrars into the list of associated
      59             : /// registrants.  This is usually used to define the
      60             : /// `creatable_classes` type list.
      61             : template <typename RegistrarList>
      62           1 : using registrants = tmpl::transform<
      63             :     tmpl::remove_duplicates<RegistrarList>,
      64             :     detail::registrant<tmpl::pin<tmpl::remove_duplicates<RegistrarList>>,
      65             :                        tmpl::_1>>;
      66             : }  // namespace Registration