c++11改进设计模式Singleton模式

c++11改进设计模式Singleton模式关于学习《深⼊应⽤c++11》的代码笔记:
c++11之前是这么实现的
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之后可以简略⼀点，使⽤了可变模板参数
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;
}。