单例模式模板
在平常的开发工作中,单例是我们经常使用的模式,经常我们需要写无数个单例类,现在提供一种单例模板:
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#pragma once // common include #include <stdio.h> #include <stdlib.h> #include <assert.h> // windows include #if defined _WIN32 #else // linux include #include <errno.h> #endif template < typename T> class Singleton { protected : static T* singleton_; public : Singleton( void ) { assert (!singleton_); #if defined(_MSC_VER) && _MSC_VER < 1200 int offset = ( int )(T*)1 - ( int )(Singleton <T>*)(T*)1; singleton_ = (T*)(( int ) this + offset); #else singleton_ = static_cast < T* >( this ); #endif } ~Singleton( void ){ assert (singleton_); singleton_ = 0; } static T& getSingleton( void ) { assert (singleton_); return (*singleton_); } static T* getSingletonPtr( void ){ return singleton_; } }; #define _SINGLETON_INIT( TYPE ) \ template <> TYPE * Singleton< TYPE >::singleton_ = 0; \ |
用法:
class A:public Singleton<A>
{
};
在cpp文件中:
template<> A* Singleton<A>::singleton_ = 0;
_SINGLETON_INIT(A)