In which cases is it correct to apply the Singleton pattern in development?

The Singleton pattern is used when it is necessary to guarantee that a class has only one instance and to provide a global access point to it.

Typical use cases:

• Managing access to resources, such as a database or application configuration.
• Loggers, so that all parts of the program write to the same log.
• Caching or connection pooling.

It is important to remember that Singleton can complicate testing and lead to multithreading issues if not implemented correctly.

Example in C++:

class Singleton {
private:
    static Singleton* instance;
    Singleton() {} // private constructor
public:
    static Singleton* getInstance() {
        if (!instance) {
            instance = new Singleton();
        }
        return instance;
    }
};

Singleton* Singleton::instance = nullptr;