Constructors and destructors

Constructors and Destructors

In C++ Object-Oriented Programming, constructors and destructors are special functions used to manage how objects are created and destroyed. They are automatically called when an object is created or deleted.

Constructor

A constructor is a special member function that is called automatically when an object is created. It is used to initialize the object’s data members.

Key Points:

• Has the same name as the class
• No return type, not even void
• Can be overloaded (you can have multiple constructors with different parameters)

Types of Constructors:

1. Default Constructor
   Takes no arguments. Used to assign default values.

   class Student {
   public:
       int age;
       Student() {
           age = 18;
       }
   };
   

2. Parameterized Constructor
   Takes arguments to initialize data with custom values.

   class Student {
   public:
       int age;
       Student(int a) {
           age = a;
       }
   };
   

3. Copy Constructor
   Initializes an object using another object of the same class.

   class Student {
   public:
       int age;
       Student(int a) { age = a; }
       Student(const Student &s) {
           age = s.age;
       }
   };
   

Destructor

A destructor is a special member function that is called automatically when an object is destroyed. It is used to release memory or clean up resources used by the object.

Key Points:

• Has the same name as the class, but with a tilde (~) in front
• Takes no arguments
• Has no return type
• Cannot be overloaded

Example:

class Student {
public:
    Student() {
        cout << "Constructor called" << endl;
    }

    ~Student() {
        cout << "Destructor called" << endl;
    }
};

When an object of Student is created, the constructor runs automatically. When the object goes out of scope or is deleted, the destructor runs.

Why Use Constructors and Destructors:

• Constructors make sure objects are set up properly when they are created.
• Destructors make sure resources like memory, files, or database connections are cleaned up when the object is no longer needed.

They help in writing efficient and safe code, especially when dealing with dynamic memory or external resources.