What is a Destructor?

A destructor is a special member function that runs automatically when an object is destroyed.

Its main job is cleanup.

Basic Rules

• The destructor name is the class name with ~ before it.
• It has no return type.
• It takes no parameters.
• It cannot be overloaded.
• It is called automatically.

Example

#include <iostream>

class Session {
public:
    Session() {
        std::cout << "Session started\n";
    }

    ~Session() {
        std::cout << "Session ended\n";
    }
};

int main() {
    {
        Session session;
    } // destructor runs here

    std::cout << "main continues\n";
}

When Does It Run?

Stack object:

{
    Session s;
} // destructor runs here

Dynamic object:

Session* s = new Session();
delete s; // destructor runs here

Smart pointer:

auto s = std::make_unique<Session>();
// destructor runs automatically when smart pointer goes out of scope

When Should You Write a Destructor?

You usually do not need to write a destructor if your class uses:

• std::string
• std::vector
• std::unique_ptr
• other RAII types

You may need a custom destructor when your class directly owns:

• raw dynamic memory
• file handles
• sockets
• operating-system resources

Manual Destructor Call?

A destructor can be called manually:

// object.~ClassName();

But normal programs should not do this. It is for advanced manual lifetime management. If the destructor runs twice for the same object, behavior can become undefined.

Viva Answer

A destructor is a special member function named with ~ClassName. It runs automatically when an object is destroyed and is used for cleanup. It has no return type, takes no parameters, and cannot be overloaded.

Quick Check

• What is destructor syntax?
• Can a destructor take parameters?
• Can a destructor be overloaded?
• When should you write a custom destructor?