Command设计模式3

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2014-11-18 星期一 20:44:45

接下来对struct TestFunctor的泛化，主要是对返回值的返回。分void和非void

1、TestFunctorImpl

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template<typename R>
struct Rtraits
{
    enum{isvoid = false};
    typedef R reltype;
};
 
template<>
struct Rtraits<void>
{
    enum{isvoid = true};
    typedef void reltype;
};
 
template<typename R, class TList>
struct TestFunctorImpl
{
    typedef R ResultType;
    typedef typename
        TypeAtNonStrict<TList, 0, NullType>::Result Parm1;
 
    typedef typename
        TypeAtNonStrict<TList, 1, NullType>::Result Parm2;
 
    typedef typename Rtraits<R>::reltype reltype;
 
    ResultType operator()(Parm1 p1, Parm2 p2)
    {
        if(Rtraits<R>::isvoid)
        {
            printf("TestFunctorImpl::operator(%d, %f) called, return void\n", p1, p2);
            return operator_(p1, p2);
        }
        else
        {
            printf("TestFunctorImpl::operator(%d, %f) called, return void not\n", p1, p2);     
            return operator_(p1,  p2, 1);
        }
    }
    ResultType operator_(Parm1 p1, Parm2 p2)
    {
        printf("TestFunctorImpl::operator1(%d, %f) called, return void\n", p1, p2);
    }
    ResultType operator_(Parm1 p1, Parm2 p2, int)
    {
        printf("TestFunctorImpl::operator1(%d, %f) called, return void not\n", p1, p2);
    }
};

2、main.cpp

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int main(int argc, char* argv[])
{
    TestFunctorImpl<void, TYPELIST_2(int , double)> fImpl;
    Functor< void, TYPELIST_2(int , double) > cmdImpl(fImpl);
    cmdImpl(5, 5.5);
    printf("\n######\n");
 
    TestFunctorImpl<int, TYPELIST_2(int , double)> fImpl_1;
    Functor< int, TYPELIST_2(int , double) > cmdImpl_1(fTmpl_1);
    cmdImpl_1(5, 5.5);
 
    return 0;
}

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