NAME

       Subject - object with views

SYNOPSIS

       #include <InterViews/subject.h>

DESCRIPTION

       A  subject  is  an  object  that  has  one  or more views that it wishes to notify when it
       changes.  The SubjectIteractor class can be used if it is necessary to iterate through the
       views of a subject explicitly.

       Because  subjects  are  shared,  Subject  is  a  subclass  of  Resource.  To allow for the
       possibility of multiple inheritance,  in  which  case  only  a  single  copy  of  resource
       information should be maintained, Resource is a virtual base class.

PUBLIC OPERATIONS

       enum UpdateHint {
           attaching, detaching, setting, changing
       }
              This  type enumerates possible hints when a subject is notifying a view that it has
              changed.  The attaching hint indicates that a view has  attached  to  the  subject.
              The  detaching  hint  means  that  the subject is being deleted and the view should
              consider itself detached.  The setting hint means that the subject's value has been
              set,  though possibly to the same value as it already has.  The changing hint means
              that the value is set to something different than it was previously.

       virtual void attach(View*)
              Add a view to the subject's list.

       virtual void detach(View*)
              Remove a view from the subject's list.

       virtual void notify(UpdateHint = changing)
              Notify all the views of a subject that it has been updated.

       virtual boolean viewed_by(View*)
              Return whether a given view is on the subject's list of views.

       virtual void Attach(Interactor*)
              This function  is  equivalent  to  attach  and  is  provided  solely  for  backward
              compatibility.  It will be removed in a future version.

       virtual void Detach(Interactor*)
              This  function  is  equivalent  to  detach  and  is  provided  solely  for backward
              compatibility.  It will be removed in a future version.

       virtual void Notify()
              This function is equivalent to notify(changing) and is provided solely for backward
              compatibility.  It will be removed in a future version.

       boolean IsView(Interactor*)
              This  function  is  equivalent  to  viewed_by  and  is provided solely for backward
              compatibility.  It will be removed in a future version.

SUBJECTITERATOR OPERATIONS

       A subject iterator can be used to iterate through the views in a subject.

       SubjectIterator(Subject*)
              Create a subject iterator for the given subject.  The iterator  is  only  valid  as
              long as the subject exists.

       virtual void init()
              Reset  the  iteration  to  start  at  the beginning of the list.  This operation is
              called by the constructor.

       virtual boolean more()
              Return whether there are more views in the list.

       virtual View* cur()
              Return the current view.

       virtual void remove()
              Remove the current view from the list.

       virtual void next()
              Move the iteration to the next view in the list.

SEE ALSO

       View(3I)