荒廢的記事本

以前在C裡面function pointer不失是一種很神祕而且很好用的工具，

而到了C++的class method的時候，卻因為overloaded-function造成這個特性的喪失，

其實也不是沒有解法的，

C的function pointer:

typedef void (*FunctionType)(int, int);

void sum(int a, int b) {

int c = a + b;

}

FunctionType fn = sum;

// calling

fn();

C++的class method pointer:

class MyClass {

public:

MyClass(int a) : mA(a) {}

...

void sum(int a, int b);

return a + b + mA;

};

...

protected:

int mA;

}

// Method is a function pointer whose type is (MyClass::*)(int, int),

// its name can be customized by you.

void (MyClass::*Method)(int, int) = &(MyClass::sum);

// calling

MyClass obj(1), o2(10);

// obj is a instance of MyClass, and the Method is just a function pointer.

int result = (obj.*)Method(2, 3);

// result is 6.

result = (o2.*)Method(9, 8);

// result is 27.

看起來很麻煩，搭配template用起來可是威力十足呢~