Re: Shallow\Deep copy

From:
Neil Butterworth <nbutterworth1953@gmail.com>
Newsgroups:
comp.lang.c++.moderated
Date:
Wed, 7 Oct 2009 06:46:29 CST
Message-ID:
<hahgu5$pd1$1@news.eternal-september.org>
ManicQin wrote:

Hi, I'll do my best to explain my problem...
I have an data type that is wrapping a vector of pointers, currently I
have no control of the type that the vector holds and I need to be as
generic as I can (it's a part of a frame work).
naturally my vector is templated by the client.

I tried to think of a way to deep copy the vector into another -

without<- adding Clone function and such to the objects and I couldnt

think of one, I would be happy if anyone knows of a way...


Presumably your class looks like this:

template <typename T>
class C {
   public:
     // stuff
   private:
     std::vector <T*> v;
};

in which case why not add a copy constructor that "deep copies" by using
the copy constructor of the things pointed to by the vector:

C( const C & c ) {
   for( int i = 0; i < c.v.size(); i++ ) {
     v.push_back( new T( *c.v.at(i) ));
   }
}

This of course does not give you polymorphic copying - if you want that,
I think forcing your clients to supply a virtual Clone() function is the
  most sensible solution.

Neil Butterworth

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