Destructor role in C++

Introduction

A destructor is a special function that cleans up when an object is no longer needed. It helps free resources like memory or files automatically.

When you want to close a file automatically after using it.

When you allocate memory during an object's life and want to free it safely.

When you want to release a network connection when an object is destroyed.

When you want to print a message or log when an object is removed.

When you want to avoid memory leaks by cleaning up resources.

Syntax

C++

class ClassName {
public:
    ~ClassName() {
        // cleanup code here
    }
};

The destructor has the same name as the class but starts with a tilde (~).

It has no return type and no parameters.

Examples

Basic destructor syntax inside a class.

C++

class MyClass {
public:
    ~MyClass() {
        // called automatically when object is destroyed
    }
};

Destructor closes a file automatically.

C++

#include <fstream>
class FileHandler {
public:
    ~FileHandler() {
        file.close(); // close file when object is destroyed
    }
private:
    std::fstream file;
};

Destructor frees memory allocated in constructor.

C++

class Buffer {
public:
    Buffer() { data = new int[10]; }
    ~Buffer() { delete[] data; }
private:
    int* data;
};

Sample Program

This program shows when the destructor runs. The object d is created inside a block and destroyed when the block ends.

C++

#include <iostream>

class Demo {
public:
    Demo() { std::cout << "Object created\n"; }
    ~Demo() { std::cout << "Destructor called: Object destroyed\n"; }
};

int main() {
    {
        Demo d;
        std::cout << "Inside block\n";
    } // d goes out of scope here
    std::cout << "Outside block\n";
    return 0;
}

Important Notes

Destructor runs automatically when an object goes out of scope or is deleted.

You cannot call a destructor directly; it is called by the system.

If you don't define a destructor, the compiler creates a default one that does nothing.

Summary

Destructor cleans up resources when an object is destroyed.

It has the same name as the class with a ~ prefix and no parameters.

Destructor runs automatically when an object goes out of scope or is deleted.