Design Patterns in C++

The same patterns covered for Java reappear in C++, expressed through smart pointers and RAII instead of garbage collection:

// Singleton, using a function-local static (thread-safe since C++11)
class AppConfig {
public:
    static AppConfig &getInstance() {
        static AppConfig instance;
        return instance;
    }

private:
    AppConfig() = default;
};

// Factory, returning ownership via unique_ptr
std::unique_ptr<Shape> createShape(const std::string &kind) {
    if (kind == "circle") return std::make_unique<Circle>(1.0);
    throw std::invalid_argument("Unknown shape: " + kind);
}

Returning std::unique_ptr<Shape> from the factory makes ownership explicit in the type signature itself — the caller receives sole ownership, with no separate documentation needed to say so.