Fire notifications when UID references are created/destroyed (senaite…

…#2061)

* Fire notifications when references are created/destroyed

* Changelog updated

* Docstring added

CHANGES.rst

@@ -5,6 +5,7 @@ Changelog
 2.3.0 (unreleased)
 ------------------
 
+- #2061 Fire notifications when UID references are created/destroyed
 - #2058 Filter 'Interpretation templates' in sample view by template and type
 - #2048 Fix catalog logging counter duplicates
 - #2047 Make resultsinterpretation.pt to retrieve departments from viewlet

src/senaite/core/events/uidreference.py

@@ -0,0 +1,52 @@
+# -*- coding: utf-8 -*-
+
+from zope.interface import implementer
+from zope.interface.interfaces import IObjectEvent
+
+
+class IUIDReferenceCreatedEvent(IObjectEvent):
+    """An event fired after a reference between two objects was cretated
+    """
+
+
+class IUIDReferenceDestroyedEvent(IObjectEvent):
+    """An event fired after a reference between two objects was destroyed
+    """
+
+
+@implementer(IUIDReferenceCreatedEvent)
+class UIDReferenceCreated(object):
+
+    def __init__(self, field, source, target):
+        """Reference Created Event
+
+        :param field: The field on the source object
+        :param source: The context object holding the UID reference field
+        :param target: The context object being referenced
+        """
+        self.field = field
+        self.source = source
+        self.target = target
+
+        # See IObjectEvent
+        # -> Allow to define an event subscriber for a custom type
+        self.object = source
+
+
+@implementer(IUIDReferenceDestroyedEvent)
+class UIDReferenceDestroyed(object):
+
+    def __init__(self, field, source, target):
+        """Reference Destroyed Event
+
+        :param field: The field on the source object
+        :param source: The context object holding the UID reference field
+        :param target: The context object being referenced
+        """
+        self.field = field
+        self.source = source
+        self.target = target
+
+        # See IObjectEvent
+        # -> Allow to define an event subscriber for a custom type
+        self.object = source

src/senaite/core/schema/configure.zcml

@@ -3,6 +3,9 @@
     i18n_domain="senaite.core">
 
   <!-- Event subscribers -->
-  <subscriber handler=".uidreferencefield.on_object_created" />
+  <subscriber
+      for="senaite.core.interfaces.IHaveUIDReferences
+           zope.lifecycleevent.interfaces.IObjectCreatedEvent"
+      handler=".uidreferencefield.on_object_created" />
 
 </configure>

src/senaite/core/schema/uidreferencefield.py

@@ -9,21 +9,33 @@
 from plone.behavior.interfaces import IBehavior
 from plone.uuid.interfaces import ATTRIBUTE_NAME
 from senaite.core import logger
+from senaite.core.events.uidreference import UIDReferenceCreated
+from senaite.core.events.uidreference import UIDReferenceDestroyed
 from senaite.core.interfaces import IHaveUIDReferences
 from senaite.core.schema.fields import BaseField
 from senaite.core.schema.interfaces import IUIDReferenceField
 from zope.annotation.interfaces import IAnnotations
-from zope.component import adapter
+from zope.event import notify
 from zope.interface import alsoProvides
 from zope.interface import implementer
-from zope.lifecycleevent.interfaces import IObjectCreatedEvent
 from zope.schema import ASCIILine
 from zope.schema import List
 
 BACKREFS_STORAGE = "senaite.core.schema.uidreferencefield.backreferences"
 
 
-@adapter(IHaveUIDReferences, IObjectCreatedEvent)
+def notify_reference_created(field, source, target):
+    """Notify that a reference between two objects was created
+    """
+    notify(UIDReferenceCreated(field, source, target))
+
+
+def notify_reference_destroyed(field, source, target):
+    """Notify that a reference between two objects was destroyed
+    """
+    notify(UIDReferenceDestroyed(field, source, target))
+
+
 def on_object_created(object, event):
     """Link backreferences after the object was created
 
@@ -41,17 +53,19 @@ def on_object_created(object, event):
         value = field.get(object)
         # handle single valued reference fields
         if api.is_object(value):
-            field.link_backref(value, object)
             logger.info(
                 "Adding back reference from %s -> %s" % (
                     value, object))
+            if field.link_backref(value, object):
+                notify_reference_created(field, object, value)
         # handle multi valued reference fields
         elif isinstance(value, list):
             for ref in value:
                 logger.info(
                     "Adding back reference from %s -> %s" % (
                         ref, object))
-                field.link_backref(ref, object)
+                if field.link_backref(ref, object):
+                    notify_reference_created(field, object, ref)
 
 
 def get_backrefs(context, relationship, as_objects=False):
@@ -208,11 +222,13 @@ def set(self, object, value):
 
         # link backreferences of new uids
         for added_obj in added_objs:
-            self.link_backref(added_obj, object)
+            if self.link_backref(added_obj, object):
+                notify_reference_created(self, object, added_obj)
 
         # unlink backreferences of removed UIDs
         for removed_obj in removed_objs:
-            self.unlink_backref(removed_obj, object)
+            if self.unlink_backref(removed_obj, object):
+                notify_reference_destroyed(self, object, removed_obj)
 
         super(UIDReferenceField, self).set(object, uids)