成員函數轉換普通函數

#include<algorithm> #include<string> using namespace std; class Widget { string name; public: Widget(string _name):name(_name) { } ~Widget() { //cout<<"goodbye:"<<name<<endl; } void Show(string &str) { cout<<str<<" say hello"<<endl; } void Display() { cout<<"running the function display"<<endl; } }; int main() { Widget wid("Shadow"); typedef void (Widget::*Function)(string &str); Function fun1=&Widget::Show; typedef void (*WidFunction)(Widget* ,string&); WidFunction fun3=WidFunction(*(reinterpret_cast<int*>(&fun1))); string str="Wang"; fun3(&wid,str); //cout<<reinterpret_cast<int*>(&fun1)<<endl; return 0; }

 以下是重新寫的模板函數

#include<algorithm>
#include<string>
#include<iostream>
using namespace std;
class Widget
{
    string name;
public:
    Widget(string _name):name(_name)
    {
    }
    ~Widget()
    {
        //cout<<"goodbye:"<<name<<endl;
    }
    void Show(string &str)
    {
        cout<<str<<" say hello"<<endl;
    }
    void Display()
    {
        cout<<"running the function display"<<endl;
    }
};
template<typename Object,typename ResultFunction,typename Function>
ResultFunction  function_cast(Function fun)
{
    ResultFunction result=ResultFunction(*(reinterpret_cast<int*>(&fun)));
    return result;
}
int main()
{
    Widget wid("Shadow");
    string str="Wang";
    typedef void (*WidFunction1)(Widget*);
    WidFunction1 fun1=function_cast<Widget,WidFunction1>(&Widget::Display);
    fun1(&wid);
    typedef void (*WidFunction2)(Widget*,string&);
    WidFunction2 fun2=function_cast<Widget,WidFunction2>(&Widget::Show);
    fun2(&wid,str);
    return 0;
}