Re: Rewriting clone() to return a boost::shared_ptr ?
helix wrote:
Hi,
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 ?
Yes, that will work fine. There is, however, one drawback, in that you
cannot use covariant return types. Consider the following:
class A
{
public:
virtual A* clone() = 0;
};
class B
{
public:
virtual B* clone(); // Covariant return type.
};
There may be cases where you have a pointer to B, and you want to clone
the object to get another pointer to B, perhaps to do something through
some B specific member functions. Only pointers and references can be
covariant, however. Consider the following:
class A
{
public:
virtual boost::shared_ptr<A> clone() = 0;
};
class B
{
public:
virtual boost::shared_ptr<B> clone(); // Can't do this! Not a pointer.
};
--
Alan Johnson
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
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