c++11 改進設計模式 Singleton模式

標籤：

關於學習 《深入應用c++11》的代碼筆記:

c++11之前是這麼實現的

template<typename T>class Singleton{public:static T* Instance(){if (m_pInstance == nullptr)m_pInstance = new T();return m_pInstance;}template<typename T0>static T* Instance(T0 arg0){if (m_pInstance == nullptr)m_pInstance = new T(arg0);return m_pInstance;}template<typename T0,typename T1>static T* Instance(T0 arg0, T1 arg1){if (m_pInstance == nullptr)m_pInstance = new T(arg0, arg1);return m_pInstance;}template<typename T0, typename T1,typename T2>static T* Instance(T0 arg0, T1 arg1,T2 arg2){if (m_pInstance == nullptr)m_pInstance = new T(arg0, arg1,arg2);return m_pInstance;}template<typename T0, typename T1, typename T2,typename T3>static T* Instance(T0 arg0, T1 arg1, T2 arg2,T3 arg3){if (m_pInstance == nullptr)m_pInstance = new T(arg0, arg1, arg2,arg3);return m_pInstance;}template<typename T0, typename T1, typename T2, typename T3,typename T4>static T* Instance(T0 arg0, T1 arg1, T2 arg2, T3 arg3,T4 arg4){if (m_pInstance == nullptr)m_pInstance = new T(arg0, arg1, arg2, arg3,arg4);return m_pInstance;}template<typename T0, typename T1, typename T2, typename T3, typename T4,typename T5>static T* Instance(T0 arg0, T1 arg1, T2 arg2, T3 arg3, T4 arg4,T5 arg5){if (m_pInstance == nullptr)m_pInstance = new T(arg0, arg1, arg2, arg3, arg4,arg5);return m_pInstance;}static T* GetInstance(){if (m_pInstance == nullptr)throw std::logic_error("the instance is not init,please init the instance first");return m_pInstance;}static void DestroyInstance(){delete m_pInstance;m_pInstance = nullptr;}private:Singleton(void);virtual ~Singleton(void);Singleton(const Singleton&);Singleton& operator = (const Singleton);static T* m_pInstance;};template<class T> T* Singleton<T>::m_pInstance = nullptr;//============================================struct A{A(){}};struct B{B(int x){}};struct C{C(int x, double y){}};int _tmain(int argc, _TCHAR* argv[]){Singleton<A>::Instance();Singleton<A>::Instance();Singleton<B>::Instance(1);Singleton<C>::Instance(1,3.14);Singleton<A>::DestroyInstance();Singleton<B>::DestroyInstance();Singleton<C>::DestroyInstance();return 0;}

　　c++11之後可以簡略一點，使用了可變模板參數

template<typename T>class Singleton{public:template <typename... Args>static T* Instance(Args&&... args){if (m_pInstance == nullptr)m_pInstance = new T(std::forward<Args>(args)...);return m_pInstance;}static T* GetInstance(){if (m_pInstance == nullptr)throw std::logic_error("the instance is not init,please initialize the instance first");return m_pInstance;}static void DestroyInstance(){delete m_pInstance;m_pInstance = nullptr;}private:Singleton(void);virtual ~Singleton(void);Singleton(const Singleton&);Singleton& operator=(const Singleton&);private:static T* m_pInstance;};template<class T>T* Singleton<T>::m_pInstance = nullptr;#include <iostream>#include <string>using namespace std;struct A{A(const string&){ cout << "lvalue" << endl; }A(string&&x){ cout << "rvalue" << endl; }};struct B{B(const string&){ cout << "lvalue" << endl; }B(string&& x){ cout << "rvalue" << endl; }};struct C{C(int x, double y){}void Fun(){ cout << "Test" << endl; }}; int _tmain(int argc, _TCHAR* argv[]){string str = "bb";Singleton<A>::Instance(str);Singleton<B>::Instance(std::move(str));Singleton<C>::Instance(1,3.14);Singleton<C>::GetInstance()->Fun();Singleton<A>::DestroyInstance();Singleton<B>::DestroyInstance();Singleton<C>::DestroyInstance();return 0;}

　　

 

c++11 改進設計模式 Singleton模式