Factory, она же — фабрика

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#include <iostream>
#include <string>
#include <map>
#include <boost/shared_ptr.hpp>

template <class base>
class factory
{
public:

    typedef boost::shared_ptr<base> base_ptr;

    template <class derived>
    void reg(std::string const& name)
    {
        factories[name] = base_type_ptr(new derived_type<derived>);
    }

    base_ptr create(std::string const& name)
    {
        return factories[name]->create();
    }

private:

    class base_type
    {
    public:

        virtual ~base_type() {}

        virtual base_ptr create() const = 0;
    };

    typedef boost::shared_ptr<base_type> base_type_ptr;

    template <class T>
    class derived_type : public base_type
    {
    public:

        virtual base_ptr create() const
        {
            return new T;
        }
    };

    typedef std::map<std::string, base_type_ptr> factory_container;

    factory_container factories;
};

class furniture
{
public:

    virtual ~furniture() {}

    virtual void show() = 0;
};

class table : public furniture
{
public:

    virtual void show()
    {
        std::cout << "The big black wooden table" << std::endl;
    }
};

class chair : public furniture
{
public:

    virtual void show()
    {
        std::cout << "The old rocking chair" << std::endl;
    }
};

int main()
{
    typedef factory<furniture> furniture_factory;
    typedef furniture_factory::base_ptr furniture_ptr;

    furniture_factory fct;

    fct.reg<table>("Table");
    fct.reg<chair>("Chair");

    furniture_ptr f1 = fct.create("Table");
    furniture_ptr f2 = fct.create("Chair");

    f1->show();
    f2->show();

    return 0;
}