handle target changes (esp deletions) via an event handler

git-svn-id: svn://svn.cy55.de/Zope3/src/loops/trunk@1046 fd906abe-77d9-0310-91a1-e0d9ade77398

README.txt

@@ -232,8 +232,16 @@ Targets
 -------
 
 We can associate a node with a concept or directly with a resource via the
-view class's target attribute:
+view class's target attribute. (We also have to supply a subscriber to
+IRelationInvalidatedEvent to make sure associated actions will be carried
+out - this is usually done through ZCML.)
 
+  >>> from loops.util import removeTargetRelation
+  >>> from loops.interfaces import ITargetRelation
+  >>> from cybertools.relation.interfaces import IRelationInvalidatedEvent
+  >>> ztapi.subscribe([ITargetRelation, IRelationInvalidatedEvent], None,
+  ...                 removeTargetRelation)
+  
   >>> m111.target = cc1
   >>> m111.target is cc1
   True
@@ -351,6 +359,22 @@ edit form provided by the node:
   >>> resources['ma07'].title
   u'Set via proxy'
 
+If the target object is removed from its container all references
+to it are removed as well. (To make this work we have to handle
+the IObjectRemovedEvent; this is usually done via ZCML in the
+cybertools.relation package.)
+
+  >>> from zope.app.container.interfaces import IObjectRemovedEvent
+  >>> from zope.interface import Interface
+  >>> from cybertools.relation.registry import invalidateRelations
+  >>> ztapi.subscribe([Interface, IObjectRemovedEvent], None,
+  ...                 invalidateRelations)
+
+  >>> del resources['ma07']
+  >>> m111.target
+  >>> IMediaAssetView.providedBy(m111)
+  False
+
 Ordering Nodes
 --------------
 

browser/configure.zcml

@@ -251,6 +251,13 @@
       add="zope.ManageContent"
       />
 
+  <menuItem
+      for="loops.interfaces.IViewManager"
+      action="contents.html"
+      permission="zope.ManageContent"
+      menu="zmi_views" title="Contents"
+      />
+    
   <!-- import/export -->
 
   <pages for="loops.interfaces.IViewManager"
@@ -298,7 +305,7 @@
       for="loops.interfaces.INode"
       template="edit.pt"
       permission="zope.ManageContent"
-      menu="zmi_views" title="Edit">
+      menu="zmi_views" title="Edit Node">
 
     <widget field="description" height="2" />
     <widget field="body" height="15" />

configure.zcml

@@ -5,7 +5,15 @@
    i18n_domain="zope"
    >
 
-  <!-- Security definitions -->
+  <!-- security definitions -->
+
+  <!-- event subscribers -->
+
+  <subscriber
+        for=".interfaces.ITargetRelation
+             cybertools.relation.interfaces.IRelationInvalidatedEvent"
+        handler=".util.removeTargetRelation"
+        />
 
   <!-- loops top-level container -->
 

interfaces.py

@@ -29,11 +29,12 @@ from zope.app.container.constraints import contains, containers
 from zope.app.container.interfaces import IContainer, IOrderedContainer
 from zope.app.file.interfaces import IImage as IBaseAsset
 from zope.app.folder.interfaces import IFolder
+from cybertools.relation.interfaces import IRelation
 
 _ = MessageFactory('loops')
 
 
-# common top-level
+# common interfaces
 
 class ILoopsObject(Interface):
     """ Common top-level interface.
@@ -56,6 +57,7 @@ class IPotentialTarget(Interface):
                                'used as a target for a view/node (and '
                                'typically specifying the corresponding schema')
 
+
 # concept interfaces
 
 class IConcept(ILoopsObject, IPotentialTarget):
@@ -335,6 +337,12 @@ class INodeConfigSchema(INode, ITargetProperties):
         required=False)
 
 
+class ITargetRelation(IRelation):
+    """ (Marker) interfaces for relations pointing to a target
+        of a view or node.
+    """
+
+
 # the loops top-level container
 
 class ILoops(ILoopsObject, IFolder):
@@ -350,4 +358,3 @@ class ILoops(ILoopsObject, IFolder):
 class ILoopsContained(Interface):
     containers(ILoops)
 
-    

util.py

@@ -22,9 +22,21 @@ Utility functions.
 $Id$
 """
 
+from zope.interface import directlyProvides, directlyProvidedBy
+from view import TargetRelation
+
+
+def removeTargetRelation(context, event):
+    """ Handles IRelationInvalidatedEvent by doing some cleanup work.
+    """
+    targetIfc = context.second.proxyInterface
+    if targetIfc:
+        directlyProvides(context.first, directlyProvidedBy(context) - targetIfc)
+
+
 def nl2br(text):
     if not text: return text
     if '\n' in text: # Unix or DOS line endings
         return '<br />\n'.join(x.replace('\r', '') for x in text.split('\n'))
-    else: # gracefully handle Mac line endigns
+    else: # gracefully handle Mac line endings
         return '<br />\n'.join(text.split('\r'))

view.py

@@ -40,6 +40,7 @@ from cybertools.relation.registry import IRelationsRegistry, getRelations
 from interfaces import IView, INode, INodeConfigSchema
 from interfaces import IViewManager, INodeContained
 from interfaces import ILoopsContained
+from interfaces import ITargetRelation
 
 
 class View(object):
@@ -74,8 +75,6 @@ class View(object):
                 return
             else:
                 registry.unregister(oldRel)
-                oldTargetSchema = oldRel.second.proxyInterface
-                directlyProvides(self, directlyProvidedBy(self) - oldTargetSchema)
                 
         if target:
             targetSchema = target.proxyInterface
@@ -157,8 +156,10 @@ class ViewManager(OrderedContainer):
 
 
 class TargetRelation(DyadicRelation):
-    """ A relation between a view and another object.
+    """ A relation between a view and its target.
     """
+    implements(ITargetRelation)
+
 
 # adapters