Home » U++ Library support » U++ Widgets - General questions or Mixed problems » why no 'Ctrl* Ctrl::Clone() const = 0' (virtual constructor)
Re: why no 'Ctrl* Ctrl::Clone() const = 0' (virtual constructor) [message #28653 is a reply to message #28381] |
Thu, 09 September 2010 10:56 |
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kohait00
Messages: 939 Registered: July 2009 Location: Germany
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Experienced Contributor |
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i tried it with the following approach, it works in MSC9 but crashed in TDMGCC, any idea why? (maybe the brute cast is inapropriate..alignment of vtable wrong or sth..)
//copyable interface, implementing the Copy function, used by PolyDeepCopyNew
template<class T, class B = EmptyClass>
class Copyable : public B
{
public:
virtual ~Copyable() {}
virtual T* Copy() const { return new T(); }
};
//this is a nice helper, meant to be used like i.e. PolyCopying<EditCtrl>
//assigning Copy'ed instances to PolyCopying<Ctrl>* with a cast, as Ctrl is direct base class of EditCtrl
template<class T>
class PolyCopying : public Copyable< PolyCopying<T>, PolyDeepCopyNew<PolyCopying<T>, T> > {};
////
PolyCopying<EditInt> abc;
PolyCopying<Ctrl>* pabc = (PolyCopying<Ctrl>*)abc.Copy();
PolyCopying<Ctrl>* pabc2 = pabc->Copy();
Add(pabc2->HSizePos().TopPos(0,100)); //crashes here
delete pabc2;
thats basicly why i need to have the Copy function in Ctrl..it makes factory cloning easy..
[Updated on: Thu, 09 September 2010 11:02] Report message to a moderator
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