Welcome to the first lesson in our Creational Design Patterns course. We are starting with a powerful and widely used pattern: the Singleton Pattern. This pattern helps ensure that a class has only one instance and provides a global point of access to it. Understanding this pattern is a fantastic first step on your journey to mastering creational design patterns.
In this lesson, you'll learn how to implement the Singleton Pattern in C++
. We'll cover the following key points:
Here's a sneak peek of the code you'll be working with:
C++1#include <iostream> 2#include <string> 3 4class Logger { 5public: 6 // Static method to access the single instance 7 static Logger& getInstance() { 8 static Logger instance; // The single instance of the Logger 9 return instance; 10 } 11 12 // Log a message to the console 13 void log(const std::string& message) { 14 std::cout << message << std::endl; 15 } 16 17private: 18 Logger() {} // Private constructor to prevent external instantiation 19 Logger(const Logger&) = delete; // Deleted copy constructor 20 void operator=(const Logger&) = delete; // Deleted assignment operator 21}; 22 23int main() { 24 // Access the Logger instance and log a message 25 Logger::getInstance().log("Singleton pattern example with Logger."); 26 return 0; 27}
In this snippet, you can see how we ensure that only one Logger
instance is created and how we access it globally. We achieve this by defining a getInstance
method that returns a reference to the single instance of the Logger
class.
These are the essential parts of the Singleton Pattern:
getInstance
method is used to access the single instance of the class without creating a new object.The Singleton Pattern offers several benefits, such as:
However, the Singleton Pattern also has some drawbacks:
The Singleton Pattern is critical for scenarios where exactly one object is needed to manage a specific task, such as logging, configuration settings, or managing database connections. By guaranteeing that only one instance of a class exists, you can avoid redundancy, save memory, and ensure consistent behavior throughout your application.
It is important to note, that even if global variables are handy they are considered unsafe, since any code can potentially modify them. Just like global variables, the Singleton Pattern provides a global point of access, but it ensures that only one instance of the class is created, protecting the instance from unwanted modifications.
Understanding and implementing the Singleton Pattern will provide you with a robust tool for managing resources efficiently. It's a simple yet powerful way to improve your program's design and reliability. Let's dive in and learn how to apply this pattern effectively.
Are you ready? Let’s start coding!