通用switch-case/if-else實現

在通信行業做事久了，經常發現在寫的程序中，大量重複出現if..else..這種嵌套層次相當深的switch寫法，所以就蒙生了自己寫一個通用switcher的想法，把這種強耦合的寫法隔離，所以就用了下面的實現

/*********************************************
 *          通用選擇器
 *  1. 適配原始函數指針
 *  2. 適配成員函數指針
 *  3. 適配仿函數
 *  4. 綁定函數
 ********************************************/
template<typename RESULT,
         typename KEY,
         typename PARA>
class switcher
{
private:
    typedef boost::function<RESULT, PARA> FUNCTOR;
public:
    void add_observer(KEY key, FUNCTOR func)
    {
        functorset.insert(make_pair(key, func));
    }
   
    RESULT match(KEY key, PARA para)
    {
        map<KEY, FUNCTOR>::const_iterator iter;
        iter = functorset.find(key);
        if (iter != functorset.end())
        {
            static_cast<FUNCTOR>(iter->second)(para);
        }
    }
private:   
    map<KEY, FUNCTOR> functorset;          
};
bool some_function(const std::string& s)
{
    std::cout << s << " This is really neat/n";
    return true;
}

class some_class
{
public:
    bool some_function(const std::string& s)
    {
        std::cout << s << " This is also quite nice/n";
        return true;
    }
};
class some_function_object
{
public:
    bool operator()(const std::string& s)
    {
        std::cout << s <<
        " This should work, too, in a flexible solution/n";
        return true;
    }
};

switcher<bool, int, string> myswitcher;

bool test(int number, string info)
{
    return myswitcher.match(number, info);
}

int main(int argv, char** argc)
{
    function1<bool,const std::string&> f1(&some_function);
    function1<bool,const std::string&> f2(&some_class::some_function,&s);
    function1<bool,const std::string&> f3(boost::bind(&some_class::some_function,&s,_1));
    some_function_object fso;
    function1<bool,const std::string&> f4(fso);
    myswitcher.add_observer(0, f1);
    myswitcher.add_observer(1, f2);
    myswitcher.add_observer(2, f3);
    myswitcher.add_observer(3, f4);
    test(0, "call by f1");
}