IFactory.h

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//  ************************************************************************************************
//
//  BornAgain: simulate and fit reflection and scattering
//
//! @file      Base/Util/IFactory.h
//! @brief     Defines interface class IFactory.
//!
//! @homepage  http://www.bornagainproject.org
//! @license   GNU General Public License v3 or higher (see COPYING)
//! @copyright Forschungszentrum Jülich GmbH 2018
//! @authors   Scientific Computing Group at MLZ (see CITATION, AUTHORS)
//
//  ************************************************************************************************
 
#ifndef USER_API
#ifndef BORNAGAIN_BASE_UTIL_IFACTORY_H
#define BORNAGAIN_BASE_UTIL_IFACTORY_H
 
#include <cassert>
#include <functional>
#include <iostream> // debug
#include <map>
#include <memory>
#include <sstream>
 
//! Base class for all factories.
 
template <class Key, class AbstractProduct>
class IFactory {
public:
    //! function which will be used to create object of AbstractProduct base type
    using CreateItemCallback = std::function<AbstractProduct*()>;
 
    //! map for correspondence between object identifier and object creation function
    using CallbackMap_t = std::map<Key, CreateItemCallback>;
 
    //! Creates object by calling creation function corresponded to given identifier
    AbstractProduct* createItem(const Key& item_key) const
    {
        auto it = m_callbacks.find(item_key);
        assert(it != m_callbacks.end());
        return (it->second)();
    }
 
    std::unique_ptr<AbstractProduct> createItemPtr(const Key& item_key) const
    {
        return std::unique_ptr<AbstractProduct>{createItem(item_key)};
    }
 
    //! Registers object's creation function
    bool registerItem(const Key& item_key, CreateItemCallback CreateFn)
    {
        assert(m_callbacks.find(item_key) == m_callbacks.end());
        return m_callbacks.insert(make_pair(item_key, CreateFn)).second;
    }
 
    bool contains(const Key& item_key) const
    {
        return m_callbacks.find(item_key) != m_callbacks.end();
    }
 
    //! Returns number of registered objects
    size_t size() const { return m_callbacks.size(); }
 
protected:
    CallbackMap_t m_callbacks; //!< map of correspondence of objectsId and creation functions
};
 
//! Returns new instance of class T.
//!
//! This templated function is used in catalogs in form of a function pointer
//! 'create_new<T>', with no function arguments supplied. Equivalently, we could
//! use a lambda function '[](){return new T;}'.
 
template <class T>
T* create_new()
{
    return new T();
}
 
#endif // BORNAGAIN_BASE_UTIL_IFACTORY_H
#endif // USER_API