c++ - 如何在多态性中强制隐式转换？

Question

请考虑这个例子，我们如何在第二个参数是指向成员函数的指针的函数中强制进行隐式转换。在函数的参数列表中显式转换不是我现在想要实现的。相反，我希望编译器以某种方式像使用 FIRST 参数那样做......

struct Base
{
    virtual ~Base() = 0 {}
};

struct Derived : public Base
{
    void f(){}
};

typedef void(Base::*polymorph)();

// how do I force IMPLICIT conversion here: EDIT: (polymorph type work only for polymorph pointer type no conversion)
void func(Base* arg1, polymorph arg2) // void* arg2, (void*) arg2 etc...  dosn't work
{
    polymorph temp = reinterpret_cast<polymorph>(arg2); // to achive this
}

int main()
{
    Derived* test = new Derived;
    // first parameter work but another gives an error
    func(test, &Derived::f); // BY NOT CHANGING THIS!
    delete test;
    return 0;
}

Answer 1

尽可能干净。下面的代码。但我不知道当实际调用“temp”时将引用谁的“this”指针。

typedef void(Base::*polymorph)(); 

void func(Base* arg1, polymorph arg2)
{ 
    polymorph temp = arg2;
} 


int main() 
{ 
    Derived* test = new Derived; 
    // first parameter work but another gives an error 
    func(test, static_cast<polymorph>(&Derived::f)); 
    delete test; 
    return 0; 
}