feat: thread-safe Singleton

Singleton/main.cpp

@@ -1,9 +1,42 @@
 #include <cstdlib>
+#include <iomanip>
 #include <iostream>
+#include <mutex>
+
+class Singleton {
+private:
+  static Singleton *singleton;
+  static std::mutex mutex;
+
+  Singleton() = default;
+
+public:
+  Singleton(const Singleton &other) = delete;
+  Singleton &operator=(const Singleton &) = delete;
+
+  static Singleton *GetInstance() {
+    std::lock_guard<std::mutex> lock(mutex);
+
+    if (singleton == nullptr) {
+      singleton = new Singleton();
+    }
+
+    return singleton;
+  }
+};
+
+Singleton *Singleton::singleton = nullptr;
+std::mutex Singleton::mutex;
 
 int main(int argc, char *argv[]) {
 
   std::cout << "Singleton" << std::endl;
 
+  auto singleton1 = Singleton::GetInstance();
+  auto singleton2 = Singleton::GetInstance();
+
+  std::cout << std::setw(20) << "Singleton 1: " << singleton1 << std::endl;
+  std::cout << std::setw(20) << "Singleton 2: " << singleton2 << std::endl;
+
   return EXIT_SUCCESS;
 }