// Use of this source code is governed by a BSD-style license
// that can be found in the License file.
//
// Author: Shuo Chen (chenshuo at chenshuo dot com)#ifndef MUDUO_BASE_SINGLETON_H
#define MUDUO_BASE_SINGLETON_H#include <boost/noncopyable.hpp>
#include <pthread.h>
#include <stdlib.h> // atexitnamespace muduo
{template<typename T>
class Singleton : boost::noncopyable
{public:static T& instance(){pthread_once(&ponce_, &Singleton::init);return *value_;}private:Singleton();~Singleton();static void init(){value_ = new T();::atexit(destroy);}static void destroy(){typedef char T_must_be_complete_type[sizeof(T) == 0 ? -1 : 1];delete value_;}private:static pthread_once_t ponce_;static T*             value_;
};template<typename T>
pthread_once_t Singleton<T>::ponce_ = PTHREAD_ONCE_INIT;template<typename T>
T* Singleton<T>::value_ = NULL;}
#endif

Singleton_test.cc

#include <muduo/base/Singleton.h>
#include <muduo/base/CurrentThread.h>
#include <muduo/base/Thread.h>#include <boost/noncopyable.hpp>
#include <stdio.h>class Test : boost::noncopyable
{public:Test(){printf("tid=%d, constructing %p\n", muduo::CurrentThread::tid(), this);}~Test(){printf("tid=%d, destructing %p %s\n", muduo::CurrentThread::tid(), this, name_.c_str());}const muduo::string& name() const { return name_; }void setName(const muduo::string& n) { name_ = n; }private:muduo::string name_;
};void threadFunc()
{printf("tid=%d, %p name=%s\n",muduo::CurrentThread::tid(),&muduo::Singleton<Test>::instance(),muduo::Singleton<Test>::instance().name().c_str());muduo::Singleton<Test>::instance().setName("only one, changed");
}int main()
{muduo::Singleton<Test>::instance().setName("only one");muduo::Thread t1(threadFunc);t1.start();t1.join();printf("tid=%d, %p name=%s\n",muduo::CurrentThread::tid(),&muduo::Singleton<Test>::instance(),muduo::Singleton<Test>::instance().name().c_str());
}

运行结果