首先放出單例模式中的程式碼:
singleton.h

#ifndef SINGLETON_H
#define SINGLETON_H
#include <iostream>
#include <mutex>

class SingleTon
{
public:
    static SingleTon * getInstance();
    void doSomething() {
        std::cout << "Do Something!" << std::endl;
    }
    ~SingleTon() { }
private
 
:
    SingleTon() { }
    static SingleTon * instance;
    static std::mutex m_mutex;

    class GC //這是一個巢狀類
    {
    public:
        ~GC() {
            //可以在這裡銷燬所有的資源
            if(instance != nullptr) {
                std::cout << "Here destroy the instance of SingleTon!" << std::endl;
 

                delete instance;
                instance = nullptr;
            }
        }
        static GC gc; //用於釋放堆記憶體中建立的單例物件
    };
};

#endif // SINGLETON_H

singleton.cpp

#include "singleton.h"

SingleTon *SingleTon::instance = nullptr; //在類外初始化靜態物件
std::mutex SingleTon::m_mutex; //在類外初始化靜態物件
SingleTon::
 
GC SingleTon::GC::gc; //在類外初始化靜態物件

SingleTon * SingleTon::getInstance() {
    if(instance == nullptr) {
        std::lock_guard<std::mutex> lock(m_mutex);
        instance = new SingleTon();
    }
    return instance;
}

main.cpp

#include "singleton.h"
#include <iostream>

int main()
{
    SingleTon::getInstance()->doSomething();
    std::cout << "The address of SingleTon instance is: " << static_cast<void *>(SingleTon::getInstance()) << std::endl;
    return 0;
}

CMakeLists.txt

cmake_minimum_required(VERSION 2.8)
set(CMAKE_CXX_STANDARD 11)
project(1-singleton3)
file(GLOB SRC *.h *.cpp)
add_executable(${PROJECT_NAME} ${SRC})

執行結果:

Do Something!
The address of SingleTon instance is: 0x2391c20
Here destroy the instance of SingleTon!