SimActivityRegistryEnroller.h

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#ifndef Notification_SimActivityRegistryEnroller_h
#define Notification_SimActivityRegistryEnroller_h
// -*- C++ -*-
//
// Package:     Notification
// Class  :     SimActivityRegistryEnroller
//
//
// Original Author:  Chris Jones
//         Created:  Sun Nov 13 15:08:12 EST 2005
//

// system include files
#include "boost/mpl/pop_back.hpp"
#include "boost/mpl/begin_end.hpp"
#include "boost/mpl/copy_if.hpp"
#include "boost/mpl/deref.hpp"
#include "boost/mpl/prior.hpp"
#include "boost/mpl/vector.hpp"
#include "boost/mpl/eval_if.hpp"
#include "boost/mpl/empty.hpp"

// user include files
#include "SimG4Core/Notification/interface/Observer.h"
#include "SimG4Core/Notification/interface/SimActivityRegistry.h"

// forward declarations
namespace enroller_helper {
  template <class T>
  struct Enrollment {
    static void enroll(SimActivityRegistry& iReg, Observer<const T*>* iObs) { iReg.connect(iObs); }
    static void enroll(SimActivityRegistry&, void*) {}
  };

  //this class is used to terminate our recursion
  template <class T>
  struct LastEnrollerHelper {
    static void enroll(SimActivityRegistry&, T*) {}
  };

  template <class T, class TVector>
  struct EnrollerHelper {
    typedef typename boost::mpl::pop_back<TVector>::type RemainingVector;
    static void enroll(SimActivityRegistry& iReg, T* iT) {
      //Try to enroll the object if it inherits from the class at the
      // end of TVector
      Enrollment<typename boost::mpl::deref<
          typename boost::mpl::prior<typename boost::mpl::end<TVector>::type>::type>::type>::enroll(iReg, iT);

      //If TVector is not at its end, call EnrollerHelper with a vector
      // that had our last type 'popped off' the end
      typedef typename boost::mpl::eval_if<
          boost::mpl::empty<TVector>,
          boost::mpl::identity<LastEnrollerHelper<T> >,
          boost::mpl::identity<EnrollerHelper<T, typename boost::mpl::pop_back<TVector>::type> > >::type NextEnroller;
      NextEnroller::enroll(iReg, iT);
    }
  };

}  // namespace enroller_helper

class SimActivityRegistryEnroller {
public:
  SimActivityRegistryEnroller() {}
  //virtual ~SimActivityRegistryEnroller();
  typedef boost::mpl::
      vector<BeginOfJob, DDDWorld, BeginOfRun, BeginOfEvent, BeginOfTrack, BeginOfStep, G4Step, EndOfTrack, EndOfEvent, EndOfRun>
          Signals;

  // ---------- const member functions ---------------------

  // ---------- static member functions --------------------
  template <class T>
  static void enroll(SimActivityRegistry& iReg, T* iObj) {
    enroller_helper::EnrollerHelper<T, Signals>::enroll(iReg, iObj);
  }
  // ---------- member functions ---------------------------

private:
  SimActivityRegistryEnroller(const SimActivityRegistryEnroller&) = delete;  // stop default

  const SimActivityRegistryEnroller& operator=(const SimActivityRegistryEnroller&) = delete;  // stop default

  // ---------- member data --------------------------------
};

#endif