02_Deep or Concrete Copy

Deep copy

In Deep copy, an object is created by copying the data of all variables and it also allocates the same size of dynamic memory with the same values to the new object. To perform a Deep copy, we need to explicitly define the copy constructor and assign dynamic memory as well, if required. It is also necessary to dynamically allocate memory to the variables in other constructors and to deallocate memory in the destructor manually using the delete keyword.

It has two sub - Divisions

• Deep copy in copy constructor
• Deep copy in assignmen operator

1) deep copy in copy constructor

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2) deep copy in assignment operator

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code example

#include <iostream>
using namespace std;
class fraction
{
    int* numerator;
    int denominator;

public:
    //---------Default  constructor-----------
    fraction()
    {
        numerator = new int(1);
        denominator = 2;
    }

    //--------Deep copy in copy constructor-----
    fraction(const fraction& tempObj)
    {
        numerator = new int;
        *numerator = *(tempObj.numerator);
        denominator = tempObj.denominator;
    }

    // -----Deep copy in assignment opeartor--
    fraction& operator==(const fraction& obj)
    {
        delete numerator; // first has to free the address that numerator already contain to prevent memory leak
        if (this != &obj) // self assignment check
        {
            numerator = new int;
            *numerator = *(obj.numerator);
            denominator = obj.denominator;
        }
        return *this; // return current obj for cascading
    }
    //---------setter------------------------
    void setNumerator(int n)
    {

        *numerator = n;
    }

    void printData() const
    {
        cout << "Rational number is: " << *numerator << "/" << denominator << endl;
    }
    // ------Destructor-----------------
    ~fraction()
    {//It is neccessary to deallocate memmory manually to prevevnt memmory leak.
        delete numerator;
    }
};
int main()
{
    fraction f1;

    fraction f2(f1); // deep copy of f1 into f2

    fraction f3 = f1; // deep copy by assignment operator

    f3.setNumerator(6); //  numerator=6 ==> of f3,but it will not change the value of numerator of f1 and f2

    //<====Test cases====>
    f3.printData();
    f1.printData();
    f2.printData();
    return 0;
}