Can you tell about design patterns you have used in your projects?

In my projects using C/C++, I have employed several common design patterns that help make the code more structured and maintainable:

• Singleton — for creating a single instance of a class, for example, for a configuration manager.
• Factory Method — for creating objects without specifying the exact class, which facilitates extension.
• Observer — for implementing a subscription and notification system, for example, in GUIs or event handling.
• RAII (Resource Acquisition Is Initialization) — a C++-specific pattern for resource management through objects, helping to prevent leaks.

Example of Singleton in C++:

class Logger {
public:
    static Logger& getInstance() {
        static Logger instance;
        return instance;
    }
    void log(const std::string& message) {
        // logging
    }
private:
    Logger() {}
    Logger(const Logger&) = delete;
    void operator=(const Logger&) = delete;
};

Using patterns helps to write more flexible and extendable code.