一个典型的体现RAII的例子

RAII是什么？

RAII是Resource Acquisition Is Initialization（wiki上面翻译成 “资源获取就是初始化”）的简称，是C++语言的一种管理资源、避免泄漏的惯用法。利用的就是C++构造的对象最终会被销毁的原则。RAII的做法是使用一个对象，在其构造时获取对应的资源，在对象生命期内控制对资源的访问，使之始终保持有效，最后在对象析构的时候，释放构造时获取的资源

来看cppreference的解释RAII
提供的示例中，lock_guard类型的lk作为栈对象，当离开作用域时销毁，自动将互斥锁m解锁。

std::mutex m;
 
void bad() 
{
    m.lock();                    // acquire the mutex
    f();                         // if f() throws an exception, the mutex is never released
    if(!everything_ok()) return; // early return, the mutex is never released
    m.unlock();                  // if bad() reaches this statement, the mutex is released
}
 
void good()
{
    std::lock_guard<std::mutex> lk(m); // RAII class: mutex acquisition is initialization
    f();                               // if f() throws an exception, the mutex is released
    if(!everything_ok()) return;       // early return, the mutex is released
}                                      // if good() returns normally, the mutex is released

以下例子在线程结束时自动析构线程对象，释放资源

Thead虚基类：

#include <pthread.h>

class Thread
{
public:
	Thread();
	virtual ~Thread();

	void Start();
	void Join();

	void SetAutoDelete(bool autoDelete);

private:
	static void* ThreadRoutine(void* arg);
	virtual void Run() = 0;
	pthread_t threadId_;
	bool autoDelete_;
};

Thread::Thread() : autoDelete_(false)
{
	cout<<"Thread ..."<<endl;
}

Thread::~Thread()
{
	cout<<"~Thread ..."<<endl;
}

void Thread::Start()
{
	pthread_create(&threadId_, NULL, ThreadRoutine, this);  //创建线程
}

void Thread::Join()
{
	pthread_join(threadId_, NULL);
}

void* Thread::ThreadRoutine(void* arg)
{
	Thread* thread = static_cast<Thread*>(arg);  //基类指针指向子类对象
	thread->Run();  //执行子类虚函数
	if (thread->autoDelete_)  //当线程执行完任务后，自行释放该对象资源
		delete thread;
	return NULL;
}

void Thread::SetAutoDelete(bool autoDelete)
{
	autoDelete_ = autoDelete;
}

继承虚基类，实现虚函数Run

class TestThread : public Thread
{
public:
	TestThread(int count) : count_(count)
	{
		cout<<"TestThread ..."<<endl;
	}

	~TestThread()
	{
		cout<<"~TestThread ..."<<endl;
	}

private:
	void Run()
	{
		while (count_--)
		{
			cout<<"this is a test ..."<<endl;
			sleep(1);
		}
	}

	int count_;
};

main函数测试

TestThread* t2 = new TestThread(5);
t2->SetAutoDelete(true);  //设置自动销毁对象
t2->Start();
t2->Join();