Re: Virtual Constructors
On Feb 27, 4:45 pm, "Victor Bazarov" <v.Abaza...@comAcast.net> wrote:
Carl R. Davies wrote:
Ok, is it because the client code might not know what the derived
class is at time of writing so it's unable to down cast?
1. Framework code declares classes Base and Derived " class Derived :
public Base "
2. So in the client code:
Derived *ptr = new Derived();
Then calls a function that only knows Base:
void func( Base *inPtr )
{
// Can't down cast because doesn't know existence of Derived
// So how does Clone() help here?
}
Apologies for being persistent, I would like to know so I can
recognise the need for "Prototype Pattern" in the future.
class clonable {
virtual clonable* clone() const = 0;
};
class Base : public clonable {
...
Base* clone() const { return new Base(*this); }
};
class Derived : public Base {
...
Derived* clone() const { return new Derived(*this); }
};
void func(Base *inPtr)
{
Base *newOne = inPtr->clone();
}
Thanks Victor, I now understand what it does and importantly "Why?".
Cheers everyone.
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