Subject: [boost] typeof or similar
From: Steffen Roeber (Steffen.Roeber_at_[hidden])
Date: 2010-02-23 04:50:59
Hi,
I have 3 classes:
1.
class Base
{
public:
virtual Base *createDerived()
{
return 0;
}
};
2.
template <class T>
class BaseT : public Base
{
public:
virtual Base *createDerived()
{
return new DerivedT<T>(); //nicht smart, because DerivedT must be known
}
};
3.
template <class T>
class DerivedT : public BaseT<T>
{
};
So far so good. Or not. But now the problems are starting.
Base *base = new BaseT<int>;
This object it created at a place that is not known where I want to create:
Base *derived = base->createDerived(); //base is a Base *
The result is an object that has the same template type as 'base'.
Finally I got my desired result, but the problem is the relation downward
relation between BaseT and DerivedT.
My preferred way would be something like a factory:
class Factory
{
public:
template <class T>
static Base *createDerived<T>()
{
return new DerivedT<T>();
}
};
But how can I tell the factory which type to be used.
Base *derived = Factory::createDerived<sameAsBase> (base); //base is a Base
*
I think there is no "normal" C++ language support. But Boost has some
methods that by-pass some language constraints. I took a loot at something
like 'typeof'. But I don't get the things together.
Has anybody any idea? Or is it impossible to do this?
Kind regards
Steffen