c++ 泛型 编程 之 Functor 设计模式

完整代码见： 

 http://download.csdn.net/detail/zhuyingqingfen/8457091

#ifndef FUNCTOR_H_#define FUNCTOR_H_#include "typelists.h"#include "typetraits.h"template<typename R,class TList>class FunctorImpl;template<typename R>class FunctorImpl<R,NullType>{public:virtual R operator()() = 0;//Clone 目的是为了产生FunctorImpl对象的一份多态(通过基类指针调用实际的对象的Clone方法)拷贝//这个也用到了“协变式返回类型"特性，即你可以在子类中改写返回值类型，指向子类(pointer to derived class)virtual FunctorImpl * Clone()const = 0;virtual ~FunctorImpl(){}//虚构造函数的作用是当删除FunctorImpl的指针时，能够调用FunctorImpl的//派生类的指针。};template<typename R,typename P1>class FunctorImpl<R,TYPELIST_1(P1)>{public:virtual R operator()(P1) = 0;virtual FunctorImpl * Clone()const = 0;virtual ~FunctorImpl(){}};template<typename R,typename P1,typename P2>class FunctorImpl<R,TYPELIST_2(P1,P2)>{public:virtual R operator()(P1,P2) = 0;virtual FunctorImpl * Clone()const = 0;virtual ~FunctorImpl(){}};template<class ParentFunctor,typename Fun>class FunctorHandler://普通函数实现public FunctorImpl<typename ParentFunctor::ResultType,typename ParentFunctor::ParmList>{public:typedef typename ParentFunctor::ResultType ResultType;FunctorHandler(const Fun & fun):_fun(fun){}FunctorHandler*Clone()const{return new FunctorHandler(*this);}ResultType operator()(){return _fun;}ResultType operator()(typename ParentFunctor::Parm1 p1){return _fun(p1);}ResultType operator()(typename ParentFunctor::Parm1 p1,typename ParentFunctor::Parm2 p2){return _fun(p1,p2);}private:Fun _fun;};template<class ParentFunctor,typename PointerToObj,typename PointerToMemFn>class MemFunHandler : public FunctorImpl<typename ParentFunctor::ResultType,typename ParentFunctor::ParmList>{public:typedef typename ParentFunctor::ResultType ResultType;MemFunHandler(const PointerToObj & pOjb,PointerToMemFn pMemFn):_pObj(pOjb),_pMemFn(pMemFn){}MemFunHandler * Clone()const {return new MemFunHandler(*this);}ResultType operator()(){return ((*_pObj).*_pMemFn)();}ResultType operator()(typename ParentFunctor::Parm1 p1){return ((*_pObj).*_pMemFn)(p1);}ResultType operator()(typename ParentFunctor::Parm1,typename ParentFunctor::Parm2){return ((*_pObj).*_pMemFn)(p1,p2);}private:PointerToObj _pObj;PointerToMemFn _pMemFn;};template<typename R,class TList>class Functor{public:typedef R ResultType;typedef TList ParmList;typedef typename TypeAtNonStrict<TList,0,EmptyType>::Result Parm1;typedef typename TypeAtNonStrict<TList,1,EmptyType>::Result Parm2;//用来处理仿函数和普通函数template<typename Fun>explicit Functor(const Fun & fun):spImpl(new FunctorHandler<Functor,Fun>(fun)){}//用来处理普通类成员函数template <class P, typename MF>explicit Functor(P const& pobj, MF memfun):spImpl(new MemFunHandler<Functor,P,MF>(pobj,memfun)){}Functor():spImpl(0){}Functor(const Functor & src){spImpl = src.spImpl?src.spImpl->Clone():NULL;}Functor& operator = (const Functor &){if (this != &src) {if (spImpl) delete spImpl;spImpl = src.spImpl? src.spImpl->Clone():NULL;}return *this;}R operator()(){return (*spImpl)();}R operator()(Parm1 p1){return (*spImpl)(p1);}R operator()(Parm1 p1,Parm2 p2){return (*spImpl)(p1,p2);}private:typedef FunctorImpl<R,TList> Impl;std::auto_ptr<Impl>spImpl;};#endif

测试：

struct TestFunctor{void operator()(int i,double d){std::cout<<"test functor:"<<i<<"  "<<d<<std::endl;}};void MysimpleFunction(int i,double d){std::cout<<"test functor:"<<i<<"  "<<d<<std::endl;}class MyClass{public:void test(int i){std::cout<<i<<std::endl;}void print(){std::cout<<"Myclass:print()"<<std::endl;}}; void functor_test(){std::cout<<"Functor Test:-----------"<<std::endl;TestFunctor f;Functor<void, TYPELIST_2(int,double)>cmd(f);typedef void (*PFun)(int,double);PFun pf  = MysimpleFunction; /*（摘自网络)按照&运算符本来的意义，它要求其操作数是一个对象，但函数名不是对象（函数是一个对象），本来&test是非法的，但很久以前有些编译器已经允许这样做， c/c++标准的制定者出于对象的概念已经有所发展的缘故，也承认了&test的合法性。 因此，对于test和&test你应该这样理解，test是函数的首地址，它的类型是void ()，&test表示一个指向函数test这个对象的地址， 它的类型是void (*)()，因此test和&test所代表的地址值是一样的，但类型不一样。test是一个函数，&test表达式的值是一个指针！ 跟此问题类似的还有对一个数组名取地址。 int a[100]; printf("%p\n", a); printf("%p\n", &a[0]); 打印值一样。 但是数组名a，指向的是具有100个int类型的组数； &a[0]指向的是元素a[0]。 即他们的值相同，但指向的类型不同*/ std::cout<<" 函数"<<MysimpleFunction<<" "<<&MysimpleFunction<<std::endl;Functor<void, TYPELIST_2(int,double)>cmd2(pf);//Functor<void, TYPELIST_2(int,double)>cmd2(&MysimpleFunction);Functor<void, TYPELIST_2(int,double)>cmd3(static_cast<PFun>(MysimpleFunction));cmd(2,3.4);cmd2(11,3.4455);cmd3(3,4.55);MyClass c;Functor<void,TYPELIST_0()> ff(&c,&MyClass::print);ff();std::cout<<"End Functor Test.........."<<std::endl;}