[Insight-developers] itkEventObject and type_info::before

[Lydia Ng]

Hi All,

In SubjectImplementation::InvokeEvent an observer
is executed if it event "the same as" (*observer)->m_Event or=20
if event is "before" (*observer)->m_Event
(see code below).

What does the "before" ordering mean?=20
Who determines this "before" ordering?
Is it consistent across platforms?=20

The only description I can on this find is:
---------------------------
You can also ask a typeinfo object if it precedes another typeinfo
object in the implementation-defined "collation sequence," using
before(typeinfo&), which returns true or false. When you say,=20

if(typeid(me).before(typeid(you))) // ...=20

you're asking if me occurs before you in the collation sequence.=20
---------------------------
(from http://www.codeguru.com/cpp/tic/tic0270.shtml)

It's not clear to me what the ordering mean? What=20
is a "collation sequence"?

In my LevelSetShapeDetectionTest I attached an
observer that response to the ProgressEvent only.

In Win32/VC++ the observer also get activated by
StartEvent. While in Cygwin/gcc the observer
was *not* activated by StartEvent.
Which behavior is correct?


Lydia



----------------------------------------------------------
void=20
SubjectImplementation::
InvokeEvent( const EventObject & event,
      Object* self)
{
  for(std::list<Observer* >::iterator i =3D m_Observers.begin();
      i !=3D m_Observers.end(); ++i)
    {
    const EventObject * e =3D  (*i)->m_Event;
    if( typeid( *e ) =3D=3D (    typeid( event ) )  ||
        typeid( *e ).before( typeid( event ) )  )
      {
      (*i)->m_Command->Execute(self, event);
      }
    }
}