oracular (3) ExternView.3U.gz

NAME

       ExternView, PreorderView, InorderView, PostorderView - base class for external representation objects and
       subclasses for common traversals

SYNOPSIS

       #include <Unidraw/Components/externview.h>

DESCRIPTION

       ExternView is the abstract base class for external representation objects.  Generally speaking,  external
       representation  objects convey domain-specific information outside the editor.  They are simply component
       views that extract information from their subject and externalize it as  a  stream  of  bytes;  thus  the
       ExternView base class is derived from ComponentView.

       There  are  three  predefined ExternView subclasses: PreorderView, InorderView, and PostorderView.  These
       subclasses manage subviews and support three common traversals of the external view hierarchy.

EXTERNVIEW PUBLIC OPERATIONS

       virtual boolean Emit(ostream&)
       virtual boolean Definition(ostream&)
              Emit and Definition make up the basic ExternView protocol.  Emit initiates external representation
              generation  and calls Definition on each of its children.  Emit normally calls the external view's
              own Definition operation first.  Then if the external view contains  subviews,  Emit  invokes  the
              children's  Definition  operations  in the proper order to ensure a syntactically correct external
              representation.  Both of these operation do nothing by default, and both  return  a  boolean  that
              indicates whether the stream of bytes was generated successfully.

       ExternView* GetView(Iterator)
       void SetView(ExternView*, Iterator&)
              These  operations do nothing by default.  Subclasses that contain children should redefine them as
              follows: GetView should return the  ExternView  to  which  an  iterator  points.   SetView  should
              initialize  the  iterator  to  point to a particular ExternView in the list of children; it should
              initialize the iterator to point to a nil instance if the given ExternView is not a child.

EXTERNVIEW PROTECTED OPERATIONS

       ExternView(Component* = nil)
              The abstract base class constructor is protected to guard against  instantiation.   It  takes  the
              subject as an optional argument.

DERIVED CLASSES

       PreorderView,  InorderView,  and  PostorderView redefine their Definition operations to perform preorder,
       inorder, and postorder traversals of their children, respectively. Each child's Definition  operation  is
       called  during  the traversal.  Note that every child must be an instance of the same ExternView subclass
       to ensure a consistent traversal order.

SEE ALSO

       Component(3U), ComponentView(3U), Iterator(3U), ostream(3C++)