Question

I have to make a library as an assignment that would implement a menu-like functionality on a linux terminal. So I have to for each submenu enable a position to be either another submenu or a call to some function.

I was wondering how to implement such a call. Since it is to be a library, it could be used to a dozen of different kinds of functions, taking different number and types of arguments.

How to implement such a method calling another functions that would not assume anything about those functions any yet could call them? Should I use templates somehow or is there another method for that; or maybe I should implement it in a whole other way?

Answer 1

You can use objects with virtual methods to do this. Then the application can decide, which parameters to put into the callback object.

class MenuItem;

// Callback Interface
struct MenuCallback
{
    virtual void activated(MenuItem* sender) = 0;
    virtual ~MenuCallback(){}
};

// Application Code
struct ConcretMenuCallback: MenuCallback
{
    ConcretMenuCallback(int parameter1);

    void activated(MenuItem* sender)
    {
        // do something with the data stored in this object
    }
};

// Example Item
class MenuItem
{
    MenuItem(MenuItem*parent, std::string caption, MenuCallback* cb);
    void notify();
}

MenuItem::notify()
{
    // call the callback-Object
    if(m_callback)
        m_callback->activated(this);
}