How Do I Call a Pointer to a Member Function in C ?

C Calling a Pointer to a Member Function

Calling a pointer to a member function in C requires specific syntax. Here's the anatomy of the syntax:

(*pointer_to_member_function)(object_pointer, arguments);

Example 1: Calling a Member Function with a Pointer

Consider the code snippet:

typedef void (Box::*HitTest) (int x, int y, int w, int h);

for (std::list<HitTest>::const_iterator i = hitTestList.begin(); i != hitTestList.end(); ++i)
{
    HitTest h = *i;
    (*h)(xPos, yPos, width, height);
}

Here, hitTestList is a list of pointers to member functions named HitTest. To call each member function using its pointer, you need to specify the this pointer, which refers to the object the function is called on. In this case, you have a pointer to a Box object box, which you can use as the this pointer:

(box->*h)(xPos, yPos, width, height);

Example 2: Adding Member Functions to a List

Consider the code snippet:

std::list<HitTest> list;

for (std::list<Box*>::const_iterator i = boxList.begin(); i != boxList.end(); ++i)
{
    Box * box = *i;
    list.push_back(&box->HitTest);
}

Here, you are adding member functions of the Box class to the list list. Note that you are taking the address of the member function using &box->HitTest.

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