StoreObjPtr.h

/**************************************************************************
 * basf2 (Belle II Analysis Software Framework)                           *
 * Author: The Belle II Collaboration                                     *
 *                                                                        *
 * See git log for contributors and copyright holders.                    *
 * This file is licensed under LGPL-3.0, see LICENSE.md.                  *
 **************************************************************************/
 
#pragma once
 
#include <framework/datastore/DataStore.h>
#include <framework/datastore/StoreAccessorBase.h>
 
#include <stdexcept>
 
namespace Belle2 {
  template <class T> class StoreObjPtr : public StoreAccessorBase {
  public:
    explicit StoreObjPtr(const std::string& name = "", DataStore::EDurability durability = DataStore::c_Event):
      StoreAccessorBase(DataStore::objectName<T>(name), durability, T::Class(), false), m_storeObjPtr(0) {}
 
    inline bool isValid() const {ensureAttached(); return m_storeObjPtr && *m_storeObjPtr;}
 
    template<class ...Args> bool construct(Args&& ... params)
    {
      T* t = new T(std::forward<Args>(params)...);
      return assign(t, false);
    }
 
    template<class ...Args> bool constructAndReplace(Args&& ... params)
    {
      T* t = new T(std::forward<Args>(params)...);
      return assign(t, true);
    }
 
    //------------------------ Imitate pointer functionality -----------------------------------------------
    inline T& operator *()  const {return *operator->();}  
    inline T* operator ->() const {ensureValid(); return static_cast<T*>(*m_storeObjPtr);}   
    inline operator bool()  const {return isValid();}   
    static std::vector<std::string> getObjectList(DataStore::EDurability durability = DataStore::c_Event)
    {
      return DataStore::Instance().getListOfObjects(T::Class(), durability);
    }
 
  private:
    inline void ensureAttached() const
    {
      if (!m_storeObjPtr) {
        const_cast<StoreObjPtr*>(this)->m_storeObjPtr = DataStore::Instance().getObject(*this);
      }
    }
    inline void ensureValid() const
    {
      ensureAttached();
      if (!m_storeObjPtr || !(*m_storeObjPtr))
        throw std::runtime_error("Trying to access StoreObjPtr " + readableName() +
                                 ", which was not created. Please check isValid() before accesses if the object is not guaranteed to be created in every event.");
    }
    TObject** m_storeObjPtr;
  };
} // end namespace Belle2