How many types of constructors in C++?

Question

Amit Mohanty · Answer

There are 3 types of Constructors. 1. Default Constructor A constructor with no arguments (or parameters) in the definition is a default constructor. Usually these constructors use to initialize data members (variables) with real values. Note: If no constructor is explicitly declared the compiler automatically creates a default constructor with no data member (variables) or initialization. Syntax of Default Constructor – class CLASS_NAME { ……… public : CLASS_NAME() //Default constructor { . . . . . . } //other member functions }; Example: #include using namespace std; //Class Name: Default_construct class Default_construct { public: int a b; // Default Constructor Default_construct() { a = 100; b = 200; } }; int main() { Default_construct con; //Object created cout 2. Parameterized Constructor Unlike Default constructor It contains parameters (or arguments) in the constructor definition and declaration. More than one argument can also pass through a parameterized constructor. Moreover these types of constructors use for overloading to differentiate between multiple constructors. Syntax – class class_Name { public: class_Name(datatype variable) //Parameterized constructor { ……………….. } }; Example: #include using namespace std; // class name: Rectangle class Rectangle { private: double length; double breadth; public: // parameterized constructor Rectangle(double l double b) { length = l; breadth = b; } double calculateArea() { return length * breadth; } }; int main() { // create objects to call constructors Rectangle obj1(106); Rectangle obj2(138); cout 3. Copy Constructor A copy constructor is a member function that initializes an object using another object of the same class. It helps to copy data from one object to another. Example – #include using namespace std; // class name: Rectangle class Rectangle { private: double length; double breadth; public: // parameterized constructor Rectangle(double l double b) { length = l; breadth = b; } // copy constructor with a Rectangle object as parameter copies data of the obj parameter Rectangle(Rectangle &obj) { length = obj.length; breadth = obj.breadth; } double calculateArea() { return length * breadth; } }; int main() { // create objects to call constructors Rectangle obj1(106); Rectangle obj2 = obj1; //copy the content using object //print areas of rectangles cout