Editing Oberon (programming language) (section)

===Method suite===
In this technique, a table of [[Subroutine|procedure]] [[Variable (computer science)|variables]] is defined and a [[global variable]] of this type is declared in the extended module and assigned back in the generic module:

 '''MODULE''' Figures; ''<span style="color: gray">(* Abstract module *)</span>''
 
 '''TYPE'''
    Figure*    = '''POINTER TO''' FigureDesc;
    Interface* = '''POINTER TO''' InterfaceDesc;
 
    InterfaceDesc* = '''RECORD'''
       draw*  : '''PROCEDURE''' (f : Figure);
       clear* : '''PROCEDURE''' (f : Figure);
       mark*  : '''PROCEDURE''' (f : Figure);
       move*  : '''PROCEDURE''' (f : Figure; dx, dy : '''<span style="color: darkblue">INTEGER</span>''');
    '''END''';
 
    FigureDesc* = '''RECORD'''
       if : Interface;
    '''END''';
 
 '''PROCEDURE''' Init* (f : Figure; if : Interface);
 '''BEGIN'''
    f.if := if
 '''END''' Init;
 
 '''PROCEDURE''' Draw* (f : Figure);
 '''BEGIN'''
    f.if.draw(f)
 '''END''' Draw;
 
 ''<span style="color: gray">(* Other procedures here *)</span>''
 
 '''END''' Figures.

We extend the generic type Figure to a specific shape:

 '''MODULE''' Rectangles;
 
 '''IMPORT''' Figures;
 
 '''TYPE'''
    Rectangle* = '''POINTER TO''' RectangleDesc;
 
    RectangleDesc* = '''RECORD'''
       (Figures.FigureDesc)
       x, y, w, h : '''<span style="color: darkblue">INTEGER</span>''';
    '''END''';
 
 '''VAR'''
    if : Figures.Interface;
 
 '''PROCEDURE''' New* ('''VAR''' r : Rectangle);
 '''BEGIN'''
    '''<span style="color: darkblue">NEW</span>'''(r);
    Figures.Init(r, if)
 '''END''' New;
 
 '''PROCEDURE''' Draw* (f : Figure);
    '''VAR'''
       r : Rectangle;
 '''BEGIN'''
    r := f(Rectangle); ''<span style="color: gray">(* f AS Rectangle *)</span>''
    ''<span style="color: gray">(* ... *)</span>''
 '''END''' Draw;
 
 <span style="color: gray">(* Other procedures here *)</span>
 
 '''BEGIN''' ''<span style="color: gray">(* Module initialisation *)</span>''
    '''<span style="color: darkblue">NEW</span>'''(if);
    if.draw  := Draw;
    if.clear := Clear;
    if.mark  := Mark;
    if.move  := Move
 '''END''' Rectangles.

[[Dynamic dispatch]] is only done via procedures in Figures module that is the generic module.