Constructor in C++ — A Complete Guide

Characteristics of a Constructor in C++

The various characteristics of constructors in C++ are:

1. The constructor name and class name are the same
2. A constructor does not have any return type
3. A constructor is called automatically once, at the time of object creation
4. Memory allocation happens when the constructor is called

Constructor Program in C++

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#include<iostream> using namespace std; class Student { public: // constructor should always be public Student(){ cout << "Constructor is being called" << endl; } }; int main(){ Student s; // constructor is called automatically return 0; }

Types of constructor in c++

There are three main types of constructors in C++:

1. Non-Parameterised Constructor

In a non-parameterized constructor, no parameters are passed to the constructor.

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class Student { public: Student(){ // no parameter is passed cout << "Constructor is being called" << endl; } };

2. Parameterised Constructor

In a parameterized constructor, values are passed to the constructor at the time of object creation.

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#include<iostream> using namespace std; class Student { public: string name; int age; Student(string name){ this->name = name; } }; int main(){ Student s("Gyan"); // constructor called with parameter return 0; }

3. Copy Constructor

A copy constructor is a special constructor in C++ used to create a new object by copying the values of an existing object.

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#include<iostream> using namespace std; class Student { public: string name; int age; Student(int age){ this->age = age; } // copy constructor Student(const Student &s){ this->age = s.age; } }; int main(){ Student s(21); Student s2 = s; cout << s2.age; // Output: 21 return 0; }

Constructor Overloading in C++

Constructor overloading is a technique of defining multiple constructors in the same class with different parameters. Each constructor performs a different type of object initialization. It is a form of compile-time polymorphism.

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class Student { public: int age; string name; Student(){ age = 18; // default age } Student(int age){ this->age = age; } Student(string name){ this->name = name; cout << "Name : " << name << endl; } };

Constructor and Normal function difference

Key Takeaways

• A constructor is automatically called when an object is created
• Constructors have the same name as the class and no return type
• There are three types: Non-Parameterized, Parameterized, and Copy Constructor
• Constructor overloading allows multiple constructors with different parameters
• Always use this-> when parameter names match class member variable names
• Constructor overloading is a form of compile-time polymorphism

Also Read

• Destructor in c++
• Encapsulation In c++
• Classes And Objects in c++
• Access Specifiers in c++