Added another example

Author: tomoss

CMakeLists.txt

@@ -6,3 +6,4 @@ add_subdirectory(singleton-meyers-example)
 add_subdirectory(singleton-classic-static-example)
 add_subdirectory(singleton-classic-dynamic-example)
 add_subdirectory(singleton-dclp-example)
+add_subdirectory(singleton-smart-pointer-example)

singleton-smart-pointer-example/CMakeLists.txt

@@ -0,0 +1,28 @@
+cmake_minimum_required(VERSION 3.21) 
+project(singleton-smart-pointer-example VERSION 0.1.0 LANGUAGES CXX)
+
+# -------------------------------------------------------------
+# Executable
+# -------------------------------------------------------------
+add_executable(singleton-smart-pointer-example
+    main.cpp
+    src/singleton.cpp
+)
+
+# -------------------------------------------------------------
+# Compiler Features
+# -------------------------------------------------------------
+target_compile_features(singleton-smart-pointer-example PRIVATE cxx_std_17)
+
+set_target_properties(singleton-smart-pointer-example PROPERTIES
+    CXX_STANDARD_REQUIRED ON
+    CXX_EXTENSIONS OFF
+)
+
+# -------------------------------------------------------------
+# Include directories
+# -------------------------------------------------------------
+# PRIVATE means: Only this target needs 'inc' to build.
+target_include_directories(singleton-smart-pointer-example PRIVATE
+    inc
+)

singleton-smart-pointer-example/inc/singleton.h

@@ -0,0 +1,14 @@
+#pragma once
+
+class Singleton {
+public:
+    Singleton(const Singleton&) = delete; /* Deleted copy constructor. */
+    Singleton& operator=(const Singleton&) = delete; /* Deleted copy assigment operator. */
+
+    static Singleton& getInstance();
+    void func();
+    ~Singleton();
+   
+private:
+    Singleton();
+};

singleton-smart-pointer-example/main.cpp

@@ -0,0 +1,32 @@
+#include "singleton.h"
+#include <iostream>
+#include <vector>
+#include <thread>
+
+/*
+* Singleton with local static unique pointer
+* Dynamic memory allocation
+* Lazy initialization
+* Singleton is created in the first call of getInstance() and destroyed automatically after main() call
+* Thread-safety IS guaranteed (C++11+)
+*/
+
+int main()
+{
+    std::cout << "--- main start ---" << std::endl;
+
+    std::vector<std::thread> threads;
+    
+    // Launch 10 threads
+    for (int i = 0; i < 10; ++i) {
+        threads.emplace_back([]() {
+            Singleton::getInstance().func();
+        });
+    }
+    
+    for (auto& t : threads) {
+        t.join();
+    }
+
+    std::cout << "--- main end ---" << std::endl;
+}

singleton-smart-pointer-example/src/singleton.cpp

@@ -0,0 +1,21 @@
+#include "singleton.h"
+#include <iostream>
+#include <memory>
+
+Singleton& Singleton::getInstance() {
+    // The "Magic Static" is thread-safe in C++11.
+    static std::unique_ptr<Singleton> instance(new Singleton());
+    return *instance;
+}
+
+Singleton::Singleton() {
+    std::cout << "Singleton created." << std::endl;
+}
+
+void Singleton::func() {
+    std::cout << "Doing something..." << std::endl;
+}
+
+Singleton::~Singleton() {
+    std::cout << "Singleton destroyed." << std::endl;
+}