Re: Maintaining stack semantics but using polymorphic code
On Apr 18, 4:57 am, "asif.lse" <asif.l...@gmail.com> wrote:
I want to specify only ONE return type in this function. I suspect I
could auto here and use decltype to declare a pointer to the returned
type so that I could assign that pointer/ref to a pointer/ref to an
abstract class for polymorphic access. I haven't read up much on these
new C++ features but could somebody help me here? I want to use stack
variables and yet want to execute polymorphic code. The problem is
that I have to specify the concrete class name and return type. So,
apparently, there is no polymorphism. I am just thinking off the top
of my head but I feel that this is very doable. Can I use templates
here?
I'll be thankful for your help.
You can use the handle/body idiom together to get there...you'll need
a prototype as well:
struct actual_class
{
virtual ~actual_class() {}
virtual void function_a() = 0;
....
void function_b() { ... } // non-virtual stuff too!!!
};
struct my_wrapper
{
void function_a() { pimpl->function_a(); }
void function_b() { pimpl->function_b(); }
....
my_wrapper(actual_class * vf) : pimpl(vf) {}
~my_wrapper() { delete pimpl; }
my_wrapper(my_wrapper const& other)
: pimpl(other.vf->clone())
{}
// assignment...
private:
actual_class * pimpl;
};
struct my_concrete_thingy : actual_class
{
// you get the idea...
};
The handle/body or pimpl idiom can actually be used to hide all kinds
of things. Inheritance, singletons...etc...
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