"Mastering C++ Design Patterns: Unraveling the Singleton Pattern ???? #CppJourneyWithLee #CPP #DesignPatterns"

Singleton Pattern: Ensuring One and Only One

The Singleton Pattern is a creational design pattern that ensures a class has only one instance and provides a global point of access to it.

When to Use:

Use the Singleton Pattern when you want to ensure a class has only one instance, and you provide a global point of access to that instance.

Implementation in C++:

class Singleton {
private:

??// Private constructor to prevent instantiation.
??Singleton() {}

// Static instance of the class.
??static Singleton* instance;

public:
??// Method to get the instance of the class.
??static Singleton* getInstance() {
????if (!instance) {
??????instance = new Singleton();
????}
????return instance;
??}
// Other methods and attributes can be added here.
};

// Initializing the static instance.
Singleton* Singleton::instance = nullptr;        

Usage:

int main() {
// Getting the Singleton instance.
??Singleton* singletonInstance = Singleton::getInstance();
// Use the instance as needed.
?return 0;
}        

Explanation:

The constructor is private, preventing the creation of instances from outside the class.

The getInstance method ensures that only one instance is created and provides global access to it.

Lazy initialization is used, creating the instance only when needed.

Benefits:

Controlled Access: The Singleton class has full control over the instantiation, ensuring that only one instance is created.

Global Point of Access: The single instance can be easily accessed globally, providing a common point for operations.

Example Scenario:

Consider a logging system where you want to maintain a single log file throughout the application. The Singleton Pattern ensures that there's only one logger instance, preventing multiple log files.

Remember, while Singleton is useful, it should be used judiciously as it introduces global state, making the system less modular and harder to test.

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