How can I use covariant return types with smart pointers?

Question

I have code like this:

class RetInterface {...}

class Ret1: public RetInterface {...}

class AInterface
{
  public:
     virtual boost::shared_ptr

        

Answer 1

There is a neat solution posted in this blog post (from Raoul Borges)

An excerpt of the bit prior to adding support for mulitple inheritance and abstract methods is:

template 
class clone_inherit : public Base
{
public:
   std::unique_ptr clone() const
   {
      return std::unique_ptr(static_cast(this->clone_impl()));
   }

private:
   virtual clone_inherit * clone_impl() const override
   {
      return new Derived(*this);
   }
};

class concrete: public clone_inherit
{
};

int main()
{
   std::unique_ptr c = std::make_unique();
   std::unique_ptr cc = b->clone();

   cloneable * p = c.get();
   std::unique_ptr pp = p->clone();
}

I would encourage reading the full article. Its simply written and well explained.