Re: Rewriting clone() to return a boost::shared_ptr ?

"Axter" <>
18 May 2006 18:32:39 -0400
helix wrote:


Are there any issues relating to writing clone() so that it returns a
smart pointer (e.g. boost::shared_ptr) rather than a raw pointer? For
example, if I have a virtual base class, A, which exposes a clone
function, and a class, B, which is dervied from A, will my 'smart'
clone() do what I expect it to do ?

class A
        virtual ~A();
        virtual boost::shared_ptr<A> clone() const = 0;

class B : public A
        virtual ~B();
        virtual boost::shared_ptr<A> clone() const;

boost::shared_ptr<A> B::clone() const
     return boost::shared_ptr<A>(new B(*this));

I recommend against using clone functions altogether, and instead use a
smart pointer that can handle cloning without requiring the target type
to have a clone function.
Consider using the following smart pointer which can do just that:

The clone function method requires more maintenance, and it's more
prone to bugs.
Consider what happens when a derived derived type gets added that
doesn't implement its own clone function.
When this happens, the object gets spliced.

For a more simplified version of the above smart pointer, check out the

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