How to implement the deep copy constructor for assignment operator using pointer..

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Actually, I tried to implement the assignment operator but it fails. Can you help me?

C++

class A
{
   public:
      int *a1;

      A()   { a1 = new int; cout<<__LINE__<<endl;   }

      A(const A *a)
      {
         if(a1)
            delete a1;
         a1 = new int;
         *a1 = *(a->a1);
         cout<<__LINE__<<endl;
      };

      A& operator = (const A &a)
      {
         if(a1)
            delete a1;
         a1 = new int;
         //a1 = *(a.a1);
         cout<<__LINE__<<endl;
         return *this;
      }
};

int main()
{
   A *a1 = new A();
   *(a1->a1) = 99;
   A *b1 = new A(a1);
   *(b1->a1) = 77;
   b1 = a1;
   cout<<*(a1->a1)<<","<<*(b1->a1)<<endl;
   cout<<a1<<","<<b1<<endl;
}

What I have tried:

Gets succeed in compile time = operator.

Posted 24-Oct-23 18:13pm

mathiv327

Updated 6-Nov-23 4:13am

Deeksha Shenoy

v2

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OriginalGriff 25-Oct-23 1:01am

"It's not working" is one of the most useless problem descriptions we get: it tells us absolutely nothing about the problem. We don't know if you get an error message, or the wrong data, or even that that code compiles successfully!
Remember that we can't see your screen, access your HDD, or read your mind - we only get exactly what you type to work with.
So tell us what happens when you run that code, what you expected to happen, how you checked what happened. Help us to help you!
Use the "Improve question" widget to edit your question and provide better information.

jeron1 25-Oct-23 10:11am

What's wrong with the answers you received the first time you asked this?
https://www.codeproject.com/Questions/5369930/How-to-implement-the-deep-copy-constructor-using-p

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KarstenK · Answer 1 · 2023-10-24T19:15:00

Clean up your code with better naming so the usage of "A" for a class name is very bad style. Use some word. And the same for the member "a". You also dont need to use a pointer for an int. That make the code much easier to understand.

I miss the assigment of your a1 member in the

C++

A& operator = (const A &a)

after the creation.

But write better code. It belongs to every code. Nobody wants to fizzle in that mess.

Rick York · Answer 2 · 2023-10-24T19:23:00

This is from a solution I posted previously for almost exactly the same question. You have fewer members this time. My answer is essentially the same this time, too. The main difference between yours and mine is I route most of it through a Set method so that I avoid duplicating code. That makes debugging much easier.

Here is the revised answer :

C++

class A
{
public:
    int * a1 { nullptr };

    A() {}                  // default constructor

    A( int x )              // assignment constructor
    {
        Set( x );
    }

    A( const A & other )    // copy constructor
    {
        Set( * other.a1 );
    }

    ~A()                        // destructor
    {
        delete a1;
        a1 = nullptr;
    }

    // copy operator

    A & operator = ( const A & other )
    {
        // prevent self-assignment

        if( this != & other )
        {
            // do copy operation

            Set( * other.a1 );
        }
        return *this;
    }

    void Set( int x )   // assignment method
    {
        if( a1 )
            delete a1;
        a1 = new int( x );
    }
};

I think it is pointless (no pun intended) to pass a pointer to an integer as an argument if you are only going access its value so I have it passed by value, not address.

How to implement the deep copy constructor for assignment operator using pointer..

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