All GendL objetcs use, or mix in, the Vanilla-Mixin* object. The full set of messages supported by this object are documented in YADD, but its worth highlighting a few in particular that are useful for application development and application debugging/inspection

Application Development

• strings-for-display - changes the display name used, for example, by Geysr to the specified string. It is specified as an inut to the object, and over-rides the default name

  (define-object name-display (base-object):objects((my-named-object :type 'box:strings-for-display "My Custom Box":length 3:width 4:height 5)))

  
• root - from anywhere in the objet tree this will return the object corrssponding to the root node

  GDL-USER> (setq self (make-object 'name-display))
  #NAME-DISPLAY #x210408140D>
  GDL-USER> (setq self (the my-named-object))
  #<BOX #x2104080FFD>
  GDL-USER> (the root)
  #NAME-DISPLAY #x210408140D>

• children - returns a list of child objects. This is equivalent to (list-elements (the)). A variant is safe-children which will return a plist with error information for an child objects which throws an error

  GDL-USER> (setq self (make-object 'name-display))
  #NAME-DISPLAY #x210408140D>
  GDL-USER> (the children)
  (#<BOX #x2104080FFD>)
  GDL-USER> (the safe-children
  (#<BOX #x2104080FFD>)
  GDL-USER> (list-elements (the))
  (#<BOX #x2104080FFD>)

• parent - returns the parent object. Care should be taken when using this message since it may impact reusability of an object if the object is used in multiple places and this is used to reference a particular slot/message in the parent object; if the object can be used by mutiple objects then it implies that slot/message must be supported wherever this is used as a child object

  GDL-USER> (setq self (make-object 'name-display))
  #NAME-DISPLAY #x210408140D>
  GDL-USER> (setq self (the my-named-object))
  #<BOX #x2104080FFD>
  GDL-USER> (the parent)
  #NAME-DISPLAY #x210408140D>

Application Debugging/Inspection

• type - returns the type of the current object

  GDL-USER> (setq self (make-object 'name-display))
  #NAME-DISPLAY #x210408140D>
  GDL-USER> (the type)
  #NAME-DISPLAY #x210408140D>
  GDL-USER> (setq self (the my-named-object))
  #<BOX #x2104080FFD>
  GDL-USER> (the type)
  #<BOX #x2104080FFD>

• all-mixins - returns a list of the mixins used by the current-object. Note that this is generated recursively, so if the mixin specified in the define-object specification itself has one or more mixins, these will be included. Any duplicates are removed

  GDL-USER> (setq self (make-object 'name-display))
  #NAME-DISPLAY #x210408140D>
  GDL-USER> (the all-mixins)
  (BASE-OBJECT VANILLA-MIXIN VANILLA-MIXIN* STANDARD-OBJECT T GENDL::GDL-BASIS)

  Note that the typep predicate examines the all-mixins list and will return t if the specified object being tested has a miixin of the type tested against. This can be particularly useful for 'tagging' objects of different types, by just mixing in an empty object and using typep against that empty object

  (define-object object-tagging (base-object):computed-slots((all-geometry (remove nil(mapcar #'(lambda(a) (when (typep a 'all-geometry-mixin) a))(the children))))(3d-shapes (remove nil(mapcar #'(lambda(a) (when (typep a '3d-shape-mixin) a))(the children))))):objects((my-box :type 'my-box:length 3:width 4:height 5)(my-sphere :type 'my-sphere:radius 4)(my-line :type 'my-line:start (make-point 0 0 0):end (make-point 10 0 0))))(define-object my-box (box3d-shape-mixinall-geometry-mixin))(define-object my-sphere (sphere3d-shape-mixinall-geometry-mixin))(define-object my-line (lineall-geometry-mixin))(define-object all-geometry-mixin())(define-object 3d-shape-mixin())

  GDL-USER> (make-self 'object-tagging)
  #<OBJECT-TAGGING #x210500014D>
  GDL-USER> (the all-geometry)
  (#<MY-BOX #x210500566D> #<MY-SPHERE #x2105004DCD> #<MY-LINE #x21050045FD>)
  GDL-USER> (the 3d-shapes)
  (#<MY-BOX #x210500566D> #<MY-SPHERE #x2105004DCD>)

Resources

	strings-for-display.lisp
	object-tagging.lisp