Re: The "widget" problem

Thomas Flynn <tflynn@gc.cuny.edu> writes:


  I am not sure whether I understand this advantage.

  To make it clear what I was thinking about, I wrote the
  following code.

  I do not see how passing the object instead of a member
  function inhibits to inherit from a button and modify it:

#include <iostream> // ::std::cout
#include <ostream> // <<
#include <vector> // ::std::vector

struct press_listener
{ virtual void pressed() = 0; };

struct button : public press_listener
{ virtual void pressed(){ ::std::cout << "pressed" << '\n'; }};

struct framework
{ ::std::vector< press_listener* >observer;
  void accept( press_listener * const listener )
  { observer.push_back( listener ); }
  void run()
  { for( press_listener * const listener : observer )
    listener->pressed(); }};

int main()
{ framework f;
  button b;
  f.accept( &b ); /* a pointer to an object is passed here
                     instead of a pointer to a member function */
  f.run(); }