All depends on how many different types and what kind of performance you need. If the number of object types are limited, then you are better off using a common base class, with specialization for each type.
The code below makes use of boost::shared_ptr
and associated cast functionality. boost::shared_dynamic_cast
can be used to cast back-and-forth between the base type and the specialized type.
#include <boost/shared_ptr.hpp>
#include <boost/make_shared.hpp>
#include <iostream>
#include <list>
namespace stackoverflow
{
struct base_object
{
enum type_t
{
directory = 0, file, link,
n_types
};
const std::string name;
const type_t type;
base_object(const std::string& name, const type_t& type) :
name(name), type(type) {
}
virtual ~base_object()
{
}
};
struct file_object : public base_object
{
file_object(const std::string& name) : base_object(name, base_object::file)
{
}
};
struct symlink_object : public base_object
{
symlink_object(const std::string& name) : base_object(name, base_object::link)
{
}
};
struct directory_object: public base_object
{
std::list<boost::shared_ptr<base_object> > children;
directory_object(const std::string& name) :
base_object(name, base_object::directory)
{
}
template < typename TypeTag >
boost::shared_ptr< typename TypeTag::object_type > add(const std::string& name);
};
template < typename ObjectType >
struct tag
{
typedef ObjectType object_type;
};
typedef tag< directory_object > directory;
typedef tag< file_object > file;
typedef tag< symlink_object > symlink;
template < typename TypeTag >
boost::shared_ptr< typename TypeTag::object_type > directory_object::add(const std::string& name)
{
return boost::shared_dynamic_cast< typename TypeTag::object_type , base_object >(
*children.insert(children.end(),
boost::shared_dynamic_cast< base_object, typename TypeTag::object_type >(
boost::make_shared< typename TypeTag::object_type >(name))));
}
} // namespace stackoverflow
int main(void)
{
using namespace stackoverflow;
boost::shared_ptr< directory_object > root = boost::make_shared< directory_object >("/");
root->add<directory>("etc")
->add<file>("hosts");
root->add<directory>("tmp")
->add<file>("something.tmp");
root->add<directory>("var")
->add<directory>("lib")
->add<directory>("mysql");
}