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    C++ Copy Constructor

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    Anshu Rajput
    The copy constructor is a special constructor that creates a new object as a copy of an existing object of the same class. It initializes the new object using the values from the existing object. The copy constructor is called when an object is returned from a function by value, passed as a parameter to a function by value, or initialized directly from another object of the same class. If a class contains dynamically allocated memory, it needs to define its own copy constructor to properly allocate memory for the new object and copy the existing object's values.

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    C++ Copy Constructor

    Uploaded by

    Anshu Rajput
    31 views4 pages
    The copy constructor is a special constructor that creates a new object as a copy of an existing object of the same class. It initializes the new object using the values from the existing object. The copy constructor is called when an object is returned from a function by value, passed as a parameter to a function by value, or initialized directly from another object of the same class. If a class contains dynamically allocated memory, it needs to define its own copy constructor to properly allocate memory for the new object and copy the existing object's values.

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    The copy constructor is a special constructor that creates a new object as a copy of an existing object of the same class. It initializes the new object using the values from the existing object. The copy constructor is called when an object is returned from a function by value, passed as a parameter to a function by value, or initialized directly from another object of the same class. If a class contains dynamically allocated memory, it needs to define its own copy constructor to properly allocate memory for the new object and copy the existing object's values.

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    © All Rights Reserved
    Download as DOCX, PDF, TXT or read online from Scribd
    Download as docx, pdf, or txt
    31 views4 pages

    C++ Copy Constructor

    Uploaded by

    Anshu Rajput
    The copy constructor is a special constructor that creates a new object as a copy of an existing object of the same class. It initializes the new object using the values from the existing object. The copy constructor is called when an object is returned from a function by value, passed as a parameter to a function by value, or initialized directly from another object of the same class. If a class contains dynamically allocated memory, it needs to define its own copy constructor to properly allocate memory for the new object and copy the existing object's values.

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    © All Rights Reserved
    Download as DOCX, PDF, TXT or read online from Scribd
    Download as docx, pdf, or txt
    of 4

    C++ Copy Constructor

    The copy constructor is a constructor which creates an object by initializing it with an


    object of the same class, which has been created previously. The copy constructor is
    used to −

     Initialize one object from another of the same type.


     Copy an object to pass it as an argument to a function.
     Copy an object to return it from a function.
    If a copy constructor is not defined in a class, the compiler itself defines one.If the class
    has pointer variables and has some dynamic memory allocations, then it is a must to
    have a copy constructor. The most common form of copy constructor is shown here −
    classname (const classname &obj) {
    // body of constructor
    }
    Here, obj is a reference to an object that is being used to initialize another object.
    #include <iostream>

    using namespace std;

    class Line {

    public:
    int getLength( void );
    Line( int len ); // simple constructor
    Line( const Line &obj); // copy constructor
    ~Line(); // destructor

    private:
    int *ptr;
    };

    // Member functions definitions including constructor


    Line::Line(int len) {
    cout << "Normal constructor allocating ptr" << endl;

    // allocate memory for the pointer;


    ptr = new int;
    *ptr = len;
    }

    Line::Line(const Line &obj) {


    cout << "Copy constructor allocating ptr." << endl;
    ptr = new int;
    *ptr = *obj.ptr; // copy the value
    }

    Line::~Line(void) {
    cout << "Freeing memory!" << endl;
    delete ptr;
    }

    int Line::getLength( void ) {


    return *ptr;
    }

    void display(Line obj) {


    cout << "Length of line : " << obj.getLength() <<endl;
    }

    // Main function for the program


    int main() {
    Line line(10);

    display(line);

    return 0;
    }

    When the above code is compiled and executed, it produces the following result −
    Normal constructor allocating ptr
    Copy constructor allocating ptr.
    Length of line : 10
    Freeing memory!
    Freeing memory!
    Let us see the same example but with a small change to create another object using
    existing object of the same type −

    #include <iostream>

    using namespace std;

    class Line {
    public:
    int getLength( void );
    Line( int len ); // simple constructor
    Line( const Line &obj); // copy constructor
    ~Line(); // destructor

    private:
    int *ptr;
    };

    // Member functions definitions including constructor


    Line::Line(int len) {
    cout << "Normal constructor allocating ptr" << endl;

    // allocate memory for the pointer;


    ptr = new int;
    *ptr = len;
    }

    Line::Line(const Line &obj) {


    cout << "Copy constructor allocating ptr." << endl;
    ptr = new int;
    *ptr = *obj.ptr; // copy the value
    }

    Line::~Line(void) {
    cout << "Freeing memory!" << endl;
    delete ptr;
    }

    int Line::getLength( void ) {


    return *ptr;
    }

    void display(Line obj) {


    cout << "Length of line : " << obj.getLength() <<endl;
    }

    // Main function for the program


    int main() {

    Line line1(10);

    Line line2 = line1; // This also calls copy constructor

    display(line1);
    display(line2);

    return 0;
    }

    When the above code is compiled and executed, it produces the following result −
    Normal constructor allocating ptr
    Copy constructor allocating ptr.
    Copy constructor allocating ptr.
    Length of line : 10
    Freeing memory!
    Copy constructor allocating ptr.
    Length of line : 10
    Freeing memory!
    Freeing memory!
    Freeing memory!

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