inheritance and polymorfism

[Tony Johansson]

Hello experts!

How is it possible to copy concrete object in a correct way without knowing
each object specific
type. Can you give some code example how this is done.

//Tony

 

[=?ISO-8859-1?Q?Stefan_N=E4we?=]

Hello experts!

How is it possible to copy concrete object in a correct way without knowing
each object specific
type. Can you give some code example how this is done.

Can you give some code example how this can not be done or what your
problem is ?

/S

 

[msalters]

Tony Johansson schreef:

Hello experts!

How is it possible to copy concrete object in a correct way without knowing
each object specific type.

What's your problem? There are at least two solutions, with templates
or
with virtual functions. Or is this homework?

Regards,
Michiel Salters

 

[Earl Purple]

Can you give some code example how this can not be done or what your
problem is ?

Given that the topic is called "inheritance and polymorphism" I assume
he is looking for a virtual clone function.

class cloneable
{
public:
virtual cloneable* clone() const = 0;
};

class ABase : public cloneable
{
// whatever stuff here
};

class ADerived : public ABase
{
public:
ADerived * clone() const { return new ADerived( *this ); }
};

class AContainer
{
private:
ABase * itsAPtr;
public:
AContainer( const AContainer& rhs )
: itsAPtr( 0 )
{
try
{
itsAPtr = rhs.itsAPtr->clone();
// anything else
}
catch ( ... )
{
delete itsAPtr;
throw;
}
}
// other stuff
};

 

[Marc Mutz]

try
{
itsAPtr = rhs.itsAPtr->clone();
// anything else
}
catch ( ... )
{
delete itsAPtr;
throw;
}

std::auto_ptr<ABase> tmp( rhs.itsAPtr->clone() );
// anything else
itsAPtr = tmp.release();

Marc