CODEWITHSUNDEEP
c++classinheritancecopy-constructor
Rob Schneider
Rob Schneider

Reputation: 165

Call copy constructors of member functions

I am trying to learn c++ and have to build a code to learn class hierarchy. It is constructed so class A and B have a has-a relationship and class B and C. I need to make a copy of my object in my main file by enabling the copy constructor of A to call the copy constructors in B and C, but I do not know how.

#ifndef A_HH
#define A_HH


#include "B.hh"


class A {
public:

  A() { std::cout << "Constructor A" << this << std::endl ; }
  A(const A&) { std::cout << "Copy Constructor A" << this << std::endl ; }
  ~A() { std::cout << "Destructor A" << this << std::endl ; }

private:


  B b;

} ;

#endif

Class B:

#ifndef B_HH
#define B_HH

#include <iostream>

#include "C.hh"

class B {
public:

  B() { std::cout << "Constructor B" << this << std::endl ;  array = new C[len];}
  B(const B& other): array(other.array) { std::cout << "Copy Constructor B" << this << std::endl ; 
   array = new C[len];
    for(int i=0;i<len;i++)
   {
       C[i] = other.C[i];
   } 

  }
  ~B() { std::cout << "Destructor B" << this << std::endl ; delete[] array;}

private:


   C *array;
   static const int len = 12;

} ;

#endif

And class C:

#ifndef C_HH
#define C_HH

#include <iostream>

class C {
public:

  C() { std::cout << "Constructor C" << this << std::endl ; }
  C(const C&) { std::cout << "Copy Constructor C" << this << std::endl ; }
  ~C() { std::cout << "Destructor C" << this << std::endl ; }

private:

} ;

#endif

I create both objects like this:

#include<iostream>
#include"A.hh"

int main(){


A a;
A a_clone(a);
}

Thus when creating a_clone, I should get the copy constructor messages, but now it is just creating a new object I think.

Follow-up question: My class B actually looks like the edited one where it has to create a dynamically allocated array of C objects. But this way it still does not use the copy constructor. How do I fix this?

Upvotes: 3

Views: 738

Answers (2)

Some programmer dude
Some programmer dude

Reputation: 409186

If you don't have a copy-constructor and let the compiler generate one for you, or if you explicitly add one and mark it as default (like e.g. A(A const&) = default;) then the generated copy-constructor should do the right thing for you.

I recommend you read about the rule of zero.

I also recommend you read about copy elision.

Upvotes: 2

piwi
piwi

Reputation: 5336

In your copy constructors you need to call the copy constructors of the members; for example:

A::A(const A& rhs): b(rhs.b) {}

Upvotes: 2

Related Questions