Singleton Pattern

The Singleton Pattern ensures that a class has only one instance and provides a global point of access to it. In modern C++, the standard way to implement this pattern is Meyers' Singleton, which is thread-safe by default.

Why Meyers' Singleton is Thread-Safe

Starting in C++11, the language standard guarantees that static local variables are initialized in a thread-safe manner:

Code Walkthrough

A thread-safe Singleton database connection pool manager.

#include <iostream>
#include <string>
class DatabaseConnector {
private:
    // 1. Private constructor to prevent direct instantiation
    DatabaseConnector() {
        std::cout << "Database Connection Established.\n";
    }
public:
    // 2. Disable copying and assignment
    DatabaseConnector(const DatabaseConnector&) = delete;
    DatabaseConnector& operator=(const DatabaseConnector&) = delete;
// 3. Thread-safe Meyers' Singleton access point
    static DatabaseConnector& getInstance() {
        static DatabaseConnector instance; // Initialized thread-safely on first execution
        return instance;
    }
void executeQuery(const std::string& query) {
        std::cout << "Executing: " << query << "\n";
    }
};
int main() {
    // Access singleton instance
    DatabaseConnector::getInstance().executeQuery("SELECT * FROM users");
    return 0;
}

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