Constructors and Destructors

This lesson covers constructors and destructors — code that runs automatically when a class instance is created or destroyed. It's for anyone searching "C++ constructor destructor."

A constructor is a member function with the same name as the class, called automatically when an instance is created, used to run initialization logic. A destructor, written ~ClassName(), is called automatically when an instance is destroyed.

The example initializes a name in the constructor, Animal(std::string n), and prints a "goodbye" message in the destructor, ~Animal().

A common early mistake is not knowing exactly when the destructor gets called. In C++, the destructor is called automatically the moment an object goes out of scope (the logic block it was declared in) — a big difference from languages with garbage collection.

In real projects, this is used as a resource-management pattern — opening a file in the constructor and reliably closing it in the destructor, for example.

📖 Reference code

#include <iostream>
#include <string>

class Animal {
public:
    std::string name;
    Animal(std::string n) {
        name = n;
        std::cout << name << " was born." << std::endl;
    }
    ~Animal() {
        std::cout << "Goodbye, " << name << "." << std::endl;
    }
};

int main() {
    Animal dog("Rex");
    std::cout << "Program about to end..." << std::endl;
    return 0;
}

✍️ Your code

Type your code, then press "Run"

🧪 This site can't compile or run C++ directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser — nothing is sent anywhere).