object-factory.h

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/*
 * Copyright (c) 2008 INRIA
 *
 * SPDX-License-Identifier: GPL-2.0-only
 *
 * Authors: Mathieu Lacage <mathieu.lacage@sophia.inria.fr>
 */
#ifndef OBJECT_FACTORY_H
#define OBJECT_FACTORY_H
 
#include "attribute-construction-list.h"
#include "object.h"
#include "type-id.h"
 
/**
 * \file
 * \ingroup object
 * ns3::ObjectFactory class declaration.
 */
 
namespace ns3
{
 
class AttributeValue;
 
/**
 * \ingroup object
 *
 * \brief Instantiate subclasses of ns3::Object.
 *
 * This class can also hold a set of attributes to set
 * automatically during the object construction.
 *
 * \see attribute_ObjectFactory
 */
class ObjectFactory
{
  public:
    /**
     * Default constructor.
     *
     * This factory is not capable of constructing a real Object
     * until it has at least a TypeId.
     */
    ObjectFactory();
    /**
     * Construct a factory for a specific TypeId by name.
     *
     * \tparam Args \deduced Template type parameter pack for the sequence of name-value pairs
     * \param [in] typeId The name of the TypeId this factory should create.
     * \param [in] args A sequence of name-value pairs of additional attributes to set.
     *
     * The args sequence can be made of any number of pairs, each consisting of a
     * name (of std::string type) followed by a value (of const AttributeValue & type).
     */
    template <typename... Args>
    ObjectFactory(const std::string& typeId, Args&&... args);
 
    /**@{*/
    /**
     * Set the TypeId of the Objects to be created by this factory.
     *
     * \param [in] tid The TypeId of the object to instantiate.
     */
    void SetTypeId(TypeId tid);
    void SetTypeId(std::string tid);
    /**@}*/
 
    /**
     * Check if the ObjectFactory has been configured with a TypeId
     *
     * \return true if a TypeId has been configured to the ObjectFactory
     */
    bool IsTypeIdSet() const;
 
    /**
     * Set an attribute to be set during construction.
     *
     * \tparam Args \deduced Template type parameter pack for the sequence of name-value pairs
     * \param [in] name The name of the attribute to set.
     * \param [in] value The value of the attribute to set.
     * \param [in] args A sequence of name-value pairs of additional attributes to set.
     *
     * The args sequence can be made of any number of pairs, each consisting of a
     * name (of std::string type) followed by a value (of const AttributeValue & type).
     */
    template <typename... Args>
    void Set(const std::string& name, const AttributeValue& value, Args&&... args);
 
    /**
     * Base case to stop the recursion performed by the templated version of this
     * method.
     */
    void Set()
    {
    }
 
    /**
     * Get the TypeId which will be created by this ObjectFactory.
     * \returns The currently-selected TypeId.
     */
    TypeId GetTypeId() const;
 
    /**
     * Create an Object instance of the configured TypeId.
     *
     * \returns A new object instance.
     */
    Ptr<Object> Create() const;
    /**
     * Create an Object instance of the requested type.
     *
     * This method performs an extra call to ns3::Object::GetObject before
     * returning a pointer of the requested type to the user. This method
     * is really syntactical sugar.
     *
     * \tparam T \explicit The requested Object type.
     * \returns A new object instance.
     */
    template <typename T>
    Ptr<T> Create() const;
 
  private:
    /**
     * Set an attribute to be set during construction.
     *
     * \param [in] name The name of the attribute to set.
     * \param [in] value The value of the attribute to set.
     */
    void DoSet(const std::string& name, const AttributeValue& value);
    /**
     * Print the factory configuration on an output stream.
     *
     * The configuration will be printed as a string with the form
     * "<TypeId-name>[<attribute-name>=<attribute-value>|...]"
     *
     * \param [in,out] os The stream.
     * \param [in] factory The ObjectFactory.
     * \returns The stream.
     */
    friend std::ostream& operator<<(std::ostream& os, const ObjectFactory& factory);
    /**
     * Read a factory configuration from an input stream.
     *
     * The configuration should be in the form
     * "<TypeId-name>[<attribute-name>=<attribute-value>|...]"
     *
     * \param [in,out] is The input stream.
     * \param [out] factory The factory to configure as described by the stream.
     * \return The stream.
     */
    friend std::istream& operator>>(std::istream& is, ObjectFactory& factory);
 
    /** The TypeId this factory will create. */
    TypeId m_tid;
    /**
     * The list of attributes and values to be used in constructing
     * objects by this factory.
     */
    AttributeConstructionList m_parameters;
};
 
std::ostream& operator<<(std::ostream& os, const ObjectFactory& factory);
std::istream& operator>>(std::istream& is, ObjectFactory& factory);
 
/**
 * \ingroup object
 * Allocate an Object on the heap and initialize with a set of attributes.
 *
 * \tparam T \explicit The requested Object type.
 * \tparam Args \deduced The type of the sequence of name-value pairs.
 * \param [in] args A sequence of name-value pairs of the attributes to set.
 * \returns A pointer to a newly allocated object.
 *
 * The args sequence can be made of any number of pairs, each consisting of a
 * name (of std::string type) followed by a value (of const AttributeValue & type).
 */
template <typename T, typename... Args>
Ptr<T> CreateObjectWithAttributes(Args... args);
 
ATTRIBUTE_HELPER_HEADER(ObjectFactory);
 
} // namespace ns3
 
/***************************************************************
 *  Implementation of the templates declared above.
 ***************************************************************/
 
namespace ns3
{
 
template <typename T>
Ptr<T>
ObjectFactory::Create() const
{
    Ptr<Object> object = Create();
    auto obj = object->GetObject<T>();
    NS_ASSERT_MSG(obj != nullptr,
                  "ObjectFactory::Create error: incompatible types ("
                      << T::GetTypeId().GetName() << " and " << object->GetInstanceTypeId() << ")");
    return obj;
}
 
template <typename... Args>
ObjectFactory::ObjectFactory(const std::string& typeId, Args&&... args)
{
    SetTypeId(typeId);
    Set(args...);
}
 
template <typename... Args>
void
ObjectFactory::Set(const std::string& name, const AttributeValue& value, Args&&... args)
{
    DoSet(name, value);
    Set(args...);
}
 
template <typename T, typename... Args>
Ptr<T>
CreateObjectWithAttributes(Args... args)
{
    ObjectFactory factory;
    factory.SetTypeId(T::GetTypeId());
    factory.Set(args...);
    return factory.Create<T>();
}
 
} // namespace ns3
 
#endif /* OBJECT_FACTORY_H */