--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/AspectVisitor.st	Fri Jun 11 19:55:26 2004 +0200
@@ -0,0 +1,135 @@
+"
+ COPYRIGHT (c) 2002 by eXept Software AG
+              All Rights Reserved
+
+ This software is furnished under a license and may be used
+ only in accordance with the terms of that license and with the
+ inclusion of the above copyright notice.   This software may not
+ be provided or otherwise made available to, or used by, any
+ other person.  No title to or ownership of the software is
+ hereby transferred.
+"
+
+"{ Package: 'stx:libbasic' }"
+
+Visitor subclass:#AspectVisitor
+	instanceVariableNames:'aspect'
+	classVariableNames:''
+	poolDictionaries:''
+	category:'System-Visiting'
+!
+
+!AspectVisitor class methodsFor:'documentation'!
+
+copyright
+"
+ COPYRIGHT (c) 2002 by eXept Software AG
+              All Rights Reserved
+
+ This software is furnished under a license and may be used
+ only in accordance with the terms of that license and with the
+ inclusion of the above copyright notice.   This software may not
+ be provided or otherwise made available to, or used by, any
+ other person.  No title to or ownership of the software is
+ hereby transferred.
+"
+!
+
+documentation
+"
+    This is a Visitor that visits only some aspects of an object.
+
+    [author:]
+        Stefan Vogel (stefan@zwerg)
+
+    [instance variables:]
+        aspect  <Symbol|Object>     something defining the aspect to be visited        
+
+    [class variables:]
+
+    [see also:]
+
+"
+! !
+
+!AspectVisitor methodsFor:'accessing'!
+
+aspect
+    "return the value of the instance variable 'aspect' (automatically generated)"
+
+    ^ aspect
+!
+
+aspect:something
+    "set the value of the instance variable 'aspect' (automatically generated)"
+
+    aspect := something.
+! !
+
+!AspectVisitor methodsFor:'helpers'!
+
+aspectElementDescriptorFor:anObject
+    "return association that should be visited for all child objects of anObject.
+     Return a collection of associations. The association key is the name of the object,
+     where the association value is the child object"
+
+    ^ anObject elementDescriptorFor:aspect.
+
+    "
+        XMLStandardCoder new aspect:#elementDescriptorForInstanceVariables;
+                 encodingOf:('blaKey' -> 'blaValue')
+
+        XMLStandardCoder new aspect:#elementDescriptorForInstanceVariables;
+                 encodingOf:('blaKey' -> nil)
+
+        XMLStandardCoder new aspect:#elementDescriptorForNonNilInstanceVariables;
+                 encodingOf:('blaKey' -> nil)
+
+        XMLStandardCoder new aspect:#blaFaselQuall;
+                 encodingOf:('blaKey' -> nil)
+    "
+!
+
+visitChildrenOf:anObject
+    "visit all child objects of anObject.
+     If aspect is defined, perform aspect to fetch the child objects.
+     Otherwise encode all the instance variables of anObject.
+
+     Subclasses may send this message"
+
+    |childObjectDescriptors|
+
+    aspect isNil ifTrue:[
+        "shortcut -- basic mechanism: visit instance variables by name"
+        super visitChildrenOf:anObject.
+        ^ self.
+    ].
+
+    childObjectDescriptors := self aspectElementDescriptorFor:anObject.
+    childObjectDescriptors do:[:association|
+        association notNil ifTrue:[
+            association value acceptVisitor:self with:association key.
+            self nextObject.
+        ].
+    ].
+
+    "
+        XMLStandardCoder new aspect:#elementDescriptorForInstanceVariables;
+                 encodingOf:('blaKey' -> 'blaValue')
+
+        XMLStandardCoder new aspect:#elementDescriptorForInstanceVariables;
+                 encodingOf:('blaKey' -> nil)
+
+        XMLStandardCoder new aspect:#elementDescriptorForNonNilInstanceVariables;
+                 encodingOf:('blaKey' -> nil)
+
+        XMLStandardCoder new aspect:#blaFaselQuall;
+                 encodingOf:('blaKey' -> nil)
+    "
+! !
+
+!AspectVisitor class methodsFor:'documentation'!
+
+version
+    ^ '$Header: /cvs/stx/stx/libbasic/AspectVisitor.st,v 1.1 2004-06-11 17:55:26 stefan Exp $'
+! !