Add foreign object in memory without saving to database

[cyberkoa@…]

Similar to the following post
​http://stackoverflow.com/questions/7908349/django-making-relationships-in-memory-without-saving-to-db?answertab=active#tab-top

class Group:
   name = models.Chars()


   def save():
       super(self, Group).save()
       # access foreign objects
       members = self.groupmember_set.all()
       
      

class GroupMember:
   group = models.ForeignKey(Group)
   member = models.ForeignKey(User)

I have a page to allow people to create Group , and invited existing user to become member.

When form is submitted, Group data and GroupMember data is submitted together.

I would like to override the Group's save function() , and in the save function(), I need to access the GroupMember data.

Example code

g = Group(name='abc')
gm1 = GroupMember(member=user1, group=g)
gm2 = GroupMember(member=user2, group=g)

g.groupmember_set.add(gm1)   # Add to memory , I do not want to save to db immediately
g.groupmember_set.add(gm2)   # Add to memory , I do not want to save to db immediately
g.save()
gm1.save()
gm2.save()

Since the .add() function save the related object to db immediately , causing error.

I do not want to save the Group object first , because it will trigger 2 times save()

[Luke Plant]

Formatting fixed, please use 'Preview' to check formatting, thanks.

If we don't save M2M objects to the DB immediately when running add(), when do we save them? save() doesn't do that, we would need a 'flush-everything-to-the-database' call, which we don't have. Adding one would require a fundamental change to the way that the ORM works - essentially something like the unit-of-work pattern in SQLAlchemy.

I'm therefore closing WONTFIX.

Note that saving the Group object first doesn't necessarily mean you need to call save() twice - the add() calls do not need to be followed by save(). (I'm guessing you may have reasons why it is this way in your case, but I don't think the situation is forced on you by Django).