C++ default constructor

A class constructor is a special member function of a class that is executed whenever we create new objects of that class.

A constructor will have exact same name as the class and it does not have any return type at all, not even void. Constructors can be very useful for setting initial values for certain member variables.

Following example explains the concept of constructor −

Example

 Live Demo

#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;
}

Output

Object is being created
Length of line : 6

Ankith Reddy

Updated on 30-Jul-2019 22:30:25

• Related Questions & Answers
• Java default constructor
• Default constructor in Java
• Default constructor in C#
• What is a default constructor in JavaScript?
• What is the default constructor in C#?
• What is default constructor in C# programs?
• What are the differences between default constructor and parameterized constructor in Java?
• How to create a default constructor in Java?
• What do you mean by default constructor in Java?
• What is the purpose of a default constructor in Java?
• Do static variables get initialized in a default constructor in java?
• Can we initialize static variables in a default constructor in Java?
• Does C++ compiler create default constructor when we write our own?
• Difference between Static Constructor and Instance Constructor in C#
• Java parameterized constructor