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Copy constructor in derived class

•

Join Date: Sep 2004

Posts: 4

Reputation: elspork is an unknown quantity at this point

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elspork

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Newbie Poster

Copy constructor in derived class

Sep 28th, 2004

I'm having a bit of trouble finding the info I need about copy constructors. Actually, I'm having a bit of trouble figuring out the right way to use them in the first place.

My question: How do I correctly call copy constructors for a derived class so that it correctly copies data from the base class as well? Here's what I've come up with.

class Base
{
Base();
Base(const Base &theObject);
int baseData;
int GetData1() const {return baseData;}
};

Base::Base(const Base &theObject)
{
baseData = theObject.GetData1() ;
}

class Derived : public Base
{
Derived();
Derived(const Derived &theObject);
int derivedData;
int GetData2() const {return baseData;}
}

Derived:: Derived( const Derived &theObject)
{
Base( &theObject );
derivedData = theObject.GetData2();
}

Is this what a copy constructor is supposed to do?

•

Join Date: Jun 2004

Posts: 436

Reputation: Chainsaw is an unknown quantity at this point

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Chainsaw

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Re: Copy constructor in derived class

Sep 28th, 2004

Ya, sorta, but you want Base( theObject ) between the declaration and the brace:

Derived:: Derived( const Derived& theObject )

: Base( theObject )

{
<further initialization>
}

(watch those &'s, they should be in the declaration, but not in the call)

•

Join Date: Sep 2004

Posts: 4

Reputation: elspork is an unknown quantity at this point

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elspork

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Newbie Poster

Re: Copy constructor in derived class

Sep 29th, 2004

hmm. still tricky, but I think I get it.

Thanks. You're my huckleberry, chainsaw.

(that's not a string of words one hears often)

•

Join Date: Sep 2009

Posts: 1

Reputation: Tarqquin is an unknown quantity at this point

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Tarqquin

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Newbie Poster

Re: Copy constructor in derived class

Sep 30th, 2009

You can also do the same for the = operator.

 Help with Code Tags 
 c Syntax (Toggle Plain Text) 
Base operator=(const Base& rhs)
{
//copy Base
}
 
Derived operator=(const Derived& rhs)
{
Base::operator=(rhs);
//copy derived
}
Base operator=(const Base& rhs)
{
//copy Base
}

Derived operator=(const Derived& rhs)
{
Base::operator=(rhs);
//copy derived
}