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Groups > comp.lang.c++ > #17225

Re: Template overriding base class virtual function?

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On Tuesday, July 24, 2012 8:26:40 AM UTC-5, Peter Davis wrote:
> If I make both Base and Cloneable be virtual base classes, this works, 
> but I don't understand why this is necessary. Why doesn't the template 
> just override the Base definition of clone()?

Because "the template" (Cloneable<Derived>) doesn't derive from Base. Try:


class Base
{
public:
  virtual Base* clone() const = 0;
};

template <typename D> class Cloneable : public Base
{
public:
  virtual Base* clone() const {
    return new D(*static_cast<const D*>(this));
  }
};

class Derived : public Cloneable<Derived>
{};

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Thread

Template overriding base class virtual function? Peter Davis <pfd@pfdstudio.com> - 2012-07-24 09:26 -0400
  Re: Template overriding base class virtual function? Casey <cartec69@gmail.com> - 2012-07-24 07:23 -0700
    Re: Template overriding base class virtual function? Noah Roberts <roberts.noah@gmail.com> - 2012-07-24 11:38 -0700
      Re: Template overriding base class virtual function? Peter Davis <pfd@pfdstudio.com> - 2012-07-25 09:06 -0400

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