C++ Programming - OOPS Concepts - Discussion

When object is created automatically constructor is declared.

Here is an example you can understand clearly :).

#include <iostream>

using namespace std;

class Line
{
public:
void setLength( double len );
double getLength( void );
Line(); // This is the constructor

private:
double length;
};

// Member functions definitions including constructor
Line::Line(void)
{
cout << "Object is being created" << endl;
}

void Line::setLength( double len )
{
length = len;
}

double Line::getLength( void )
{
return length;
}
// Main function for the program
int main( )
{
Line line;

// set line length
line.setLength(6.0);
cout << "Length of line : " << line.getLength() <<endl;

return 0;
}

By default a constructor is immediately called as soon as an object is created.

The constructor is a special member function of a class which is called/invoked when the object is created. It has the same name as that of a class.

A constructor is called at the time of declaration of an object.

class A {};
class C /* declaration of a class */
{
A a_; /* declaration of an object (but not definition) of type A */
};

will call the constructor of A?

constructor is called at the time of object creation.

#include<iostream>
using namespace std;
class A
{
public:
A()
{
cout<<"constructor"<<endl;
}
}
int main()
{
A b1;
}