C++ 单例模式

标签：singleton   单例模式   c++单例模式   

flyfish 2014-12-16

编写一个Singleton类

经过编译器处理后,C++编译器默认编写的函数代码如下

class Singleton()     
{
public:
	Singleton() {}                                 // 1 构造函数
	Singleton(const Singleton& s{}                 // 2 拷贝构造函数
	~Singleton(){}                                 // 3 析构函数
	Singleton& operator=(const Singleton& s{}      // 4 拷贝赋值函数 copy assignment
};

2 用户可以调用 

利用public成员函数来进行访问

class Singleton
{
public:
	static Singleton& getInstance()
	{
		static Singleton    instance;
		return instance;
	}
private:
	Singleton() {};
	Singleton(Singleton const&);
	void operator=(Singleton const&);
};

class noncopyable
{
protected:
	noncopyable() {}
	~noncopyable() {}

private:
	noncopyable( const noncopyable& );
	noncopyable& operator=( const noncopyable& );
};


typedef noncopyable_::noncopyable noncopyable;

class singleton_module : public boost::noncopyable
{
private:
	static bool & get_lock(){
		static bool lock = false;
		return lock;
	}
public:
	static void lock(){
		get_lock() = true;
	}
	static void unlock(){
		get_lock() = false;
	}
	static bool is_locked() {
		return get_lock();
	}
};

template<class T>
class singleton_wrapper : public T
{
public:
	static bool m_is_destroyed;
	~singleton_wrapper(){
		m_is_destroyed = true;
	}
};

template<class T>
bool detail::singleton_wrapper< T >::m_is_destroyed = false;



template <class T>
class singleton : public singleton_module
{
private:
	static T & instance;

	static void use(T const &) {}
	static T & get_instance() {
		static detail::singleton_wrapper< T > t;

		BOOST_ASSERT(! detail::singleton_wrapper< T >::m_is_destroyed);
		use(instance);
		return static_cast<T &>(t);
	}
public:
	static T & get_mutable_instance(){
		BOOST_ASSERT(! is_locked());
		return get_instance();
	}
	static const T & get_const_instance(){
		return get_instance();
	}
	static bool is_destroyed(){
		return detail::singleton_wrapper< T >::m_is_destroyed;
	}
};

template<class T>
T & singleton< T >::instance = singleton< T >::get_instance();

C++ 单例模式

标签：singleton   单例模式   c++单例模式   

原文地址：http://blog.csdn.net/flyfish1986/article/details/41967387