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Sunday, April 26, 2020

CONSTRUCTOR IN C++

Constructors in C++
What is constructor?
A constructor is a member function of a class which initializes objects of a class. In C++, Constructor is automatically called when object(instance of class) create. It is special member function of the class.
How constructors are different from a normal member function?
A constructor is different from normal functions in following ways:
·         Constructor has same name as the class itself
·         Constructors don’t have return type
·         A constructor is automatically called when an object is created.
·         If we do not specify a constructor, C++ compiler generates a default constructor for us (expects no parameters and has an empty body).

Types of Constructors:-
1.     Default Constructor
2.     Parameterized Constructor
3.     Copy Constructor

1.     Default Constructors: Default constructor is the constructor which doesn’t take any argument. It has no parameters.

#include
using namespace std;
  
class construct {
public:    int a, b;
  
    // Default Constructor
    construct()
    {
        a = 10;
        b = 20;
    }
};
  
int main()
{
    // Default constructor called automatically
    // when the object is created
    construct c;
    cout << "a: " << c.a << endl
         << "b: " << c.b; 
    return 1;
}
Output:
a: 10
b: 20
Note: Even if we do not define any constructor explicitly, the compiler will automatically provide a default constructor implicitly.
2.     Parameterized Constructors: It is possible to pass arguments to constructors. Typically, these arguments help initialize an object when it is created. To create a parameterized constructor, simply add parameters to it the way you would to any other function. When you define the constructor’s body, use the parameters to initialize the object.

#include
using namespace std;
  
class Point {
private:
    int x, y;
  
public:
    // Parameterized Constructor
    Point(int x1, int y1)
    {
        x = x1;
        y = y1;
    }
  
    int getX()
    {
        return x;
    }
    int getY()
    {
        return y;
    }
};
  
int main()
{
    // Constructor called
    Point p1(10, 15);
  
    // Access values assigned by constructor
    cout << "p1.x = " << p1.getX() << ", p1.y = "<< p1.getY();
  
    return 0;
}
Output:
p1.x = 10, p1.y = 15
Uses of Parameterized constructor:
1.     It is used to initialize the various data elements of different objects with different values when they are created.
2.     It is used to overload constructors.

.
3. Copy constructor:-
A copy constructor is a member function which initializes an object using another object of the same class. A copy constructor has the following general function prototype:
   
ClassName (ClassName &obj);
Following is a simple example of copy constructor.
include
using namespace std;
  
class Point
{
private:
    int x, y;
public:
    Point(int x1, int y1)
    { x = x1; y = y1; }
  
    // Copy constructor
    Point(Point &p2) {x = p2.x; y = p2.y; }
  
    int getX()            {  return x; }
    int getY()            {  return y; }
};
  
int main()
{
    Point p1(10, 15); // Normal constructor is called here
    Point p2 = p1; // Copy constructor is called here 
  
    // Let us access values assigned by constructors
 cout << "p1.x = " << p1.getX() << ", p1.y = " << p1.getY();
 cout << "\np2.x = " << p2.getX() << ", p2.y = " << p2.getY();
  
    return 0;
}
Output:
p1.x = 10, p1.y = 15
p2.x = 10, p2.y = 15
                                                                                                Thanks.   By Md Altaf Raja.

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