How Do I Call Pointers to Member Functions in C ?

Calling Pointer to Member Functions in C

In C , pointers to member functions provide a convenient way to dynamically invoke methods on objects. However, their syntax can be challenging.

Syntax for Calling Pointers to Member Functions

To call a pointer to a member function, the following syntax is used:

(object->*pointer_variable)(params)

where:

• object is the instance on which the function is being called
• *pointer_variable is the pointer to the member function
• params are the parameters passed to the function

Syntax Example

Consider the following 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;
    (box->*h)(xPos, yPos, width, height);
}

In this example, a list of pointers to HitTest member functions is iterated over. Each pointer is fetched from the list and invoked by providing the box pointer as this.

Adding Member Functions to a List of Pointers

To add member functions to a list of pointers, the following syntax can be used:

list.push_back(&box->HitTest);

This code pushes the pointer to the HitTest member function of the box object into the list.

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