Re: Copy Constructor

From:

Thomas Matthews <Thomas_Really_Hates_Spam@matthews.cox.net>

Newsgroups:

comp.lang.c++

Date:

Mon, 02 Apr 2007 23:18:51 -0700

Message-ID:

<RlmQh.136570$907.120336@newsfe13.phx>

john wrote:

Hey guys,

Thank you for your input from the last topic. I tried referencing my c+
+ book and googled the topic but i'am still confused a bit. I have
another problem with that same code. I was hinted what i needed all
along was a copy constructor for class A.

Class B contains a = new A(x) in it's constructor. This is good but
this doesn't make sense. Does that really fit the specs of either
construtors of class A?? So i was brought into the area of making a
copy constructor for class A. This is where i'am having problems i
made one that creates a copy of n but i cannot of x it does not
consider x a member of class A. Do i need to use pointer this?? Code
below.

#include <iostream>
using namespace std;

class A
{
  int n ;
  public:
   A():n(0)
   {
   }
   A(int x):n(x)
   {
    n = x;

Redundant. The initializer list is accomplishing the same thing
as n = x, usually more efficient.

   }

   void print()
   { cout << n<<"\n\n";
   }

    A(const A& objectCopy){

            n = objectCopy.n; // copy constructor
    }

You can make use of initializer lists for copy constructors too.
   A(const A& new_a)
     : n(new_a.n)
   {
   }

   };

   class B
   {
    A * a;

     public:

    B(A & x)
      {
      a = new A(x);
        }

You can make use of initializer lists here too.
    B(A& x)
     : a(new A(x))
    {
    }

[snip]

//--------------------------------------------------------------------------------

Thanks guys,

John

--
Thomas Matthews

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