Posted in C++/Python

Constructors & Destructors

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).

Let us understand the types of constructors in C++ by taking a real-world example. Suppose you went to a shop to buy a marker. When you want to buy a marker, what are the options? The first one you go to a shop and say give me a marker. So just saying give me a marker mean that you did not set which brand name and which color, you didn’t mention anything just say you want a marker. So when we said just I want a marker so whatever the frequently sold marker is there in the market or in his shop he will simply hand over that. And this is what a default constructor is! The second method you go to a shop and say I want a marker a red in color and XYZ brand. So you are mentioning this and he will give you that marker. So in this case you have given the parameters. And this is what a parameterized constructor is! Then the third one you go to a shop and say I want a marker like this(a physical marker on your hand). So the shopkeeper will see that marker. Okay, and he will give a new marker for you. So copy of that marker. And that’s what copy constructor is!
Types of Constructors

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

// Cpp program to illustrate the
// concept of Constructors

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


My name is Truong Thanh, graduated Master of Information Technology and Artificial Intelligent in Frankfurt University,Germany. I create this Blog to share my experience about life, study, travel...with friend who have the same hobbies.

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