magic-removal: Refs #1407 -- Added remove() and clear() methods for ForeignKeys that allow nulls.

git-svn-id: http://code.djangoproject.com/svn/django/branches/magic-removal@2434 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/fields/related.py

@@ -141,6 +141,24 @@ class ForeignRelatedObjectsDescriptor(object):
                 return new_obj
             create.alters_data = True
 
+            # remove() and clear() are only provided if the ForeignKey can have a value of null.
+            if rel_field.null:
+                def remove(self, *objs):
+                    val = getattr(instance, rel_field.rel.get_related_field().attname)
+                    for obj in objs:
+                        if getattr(obj, rel_field.attname) == val:
+                            setattr(obj, rel_field.attname, None)
+                            obj.save()
+                        else:
+                            raise rel_field.rel.to.DoesNotExist, "'%s' is not related to '%s'." % (obj, instance)
+                add.alters_data = True
+                
+                def clear(self):
+                    for obj in self.all():
+                        setattr(obj, rel_field.attname, None)
+                        obj.save()
+                add.alters_data = True
+                    
         manager = RelatedManager()
         manager.core_filters = {'%s__pk' % rel_field.name: getattr(instance, rel_field.rel.get_related_field().attname)}
         manager.model = self.related.model

tests/modeltests/many_to_one/models.py

@@ -71,6 +71,12 @@ John's second story
 >>> r2.article_set.all()
 [Paul's story]
 
+# Reporter cannot be null - there should not be a clear or remove method
+>>> hasattr(r2.article_set, 'remove')
+False
+>>> hasattr(r2.article_set, 'clear')
+False
+
 # Reporter objects have access to their related Article objects.
 >>> r.article_set.order_by('pub_date')
 [This is a test, John's second story]

tests/modeltests/many_to_one_null/models.py

@@ -20,6 +20,9 @@ class Article(models.Model):
     def __repr__(self):
         return self.headline
 
+    class Meta:
+        ordering = ('headline',)
+        
 API_TESTS = """
 # Create a Reporter.
 >>> r = Reporter(name='John Smith')
@@ -79,4 +82,40 @@ DoesNotExist
 # To retrieve the articles with no reporters set, use "reporter__isnull=True".
 >>> Article.objects.filter(reporter__isnull=True)
 [Third]
+
+# Set the reporter for the Third article
+>>> r.article_set.add(a3)
+>>> r.article_set.all()
+[First, Second, Third]
+
+# Remove an article from the set, and check that it was removed.
+>>> r.article_set.remove(a3)
+>>> r.article_set.all()
+[First, Second]
+>>> Article.objects.filter(reporter__isnull=True)
+[Third]
+
+# Create another article and reporter
+>>> r2 = Reporter(name='Paul Jones')
+>>> r2.save()
+>>> a4 = r2.article_set.create(headline='Fourth')
+>>> r2.article_set.all()
+[Fourth]
+
+# Try to remove a4 from a set it does not belong to
+>>> r.article_set.remove(a4)
+Traceback (most recent call last):
+...
+DoesNotExist: 'Fourth' is not related to 'John Smith'.
+
+>>> r2.article_set.all()
+[Fourth]
+
+# Clear the rest of the set
+>>> r.article_set.clear()
+>>> r.article_set.all()
+[]
+>>> Article.objects.filter(reporter__isnull=True)
+[First, Second, Third]
+
 """