This is actually a pretty good solution and I totally forgot about it! It will help people for sure!
On Saturday, July 23, 2016 at 1:29:42 AM UTC+3, mishbah wrote: > > While I was waiting for suggestions, I did some more research learnt about > django Conditional Expressions. > > Docs: > https://docs.djangoproject.com/en/1.9/ref/models/conditional-expressions/ > > from django.contrib.auth.models import User > from django.db.models import BooleanField > from django.db.models import When, Case, Value > > > query = When(groups__name__in=[CUSTOMER_GROUP_NAME, ], then=Value(1)) > qs2 = User.objects.annotate( > is_customer=Case(query, default=Value(0), > output_field=BooleanField())) > > > Posting it here.. someone else may find it helpful. > > On Friday, 22 July 2016 22:02:09 UTC+1, mishbah wrote: >> >> You are awesome! Thank you! >> >> On Friday, 22 July 2016 21:41:58 UTC+1, Todor Velichkov wrote: >>> >>> Hello, I don't think sub-classing `Func` would be appropriate here. A >>> much easier way would be to use `RawSQL >>> <https://docs.djangoproject.com/en/1.8/ref/models/expressions/#raw-sql-expressions> >>> ` >>> >>> since you want to dynamically check for different group you could write >>> a factory method to build `RawSQLs` for you, something like: >>> >>> from django.db.models import BooleanField >>> from django.db.models.expressions import RawSQL >>> >>> def build_has_group_raw_sql(group_name): >>> return RawSQL("""EXISTS( >>> SELECT 1 FROM `auth_group` >>> WHERE `auth_group`.`name` = %s >>> AND `auth_group`.`id` IN ( >>> SELECT `auth_user_groups`.`group_id` >>> FROM `auth_user_groups` >>> WHERE `auth_user_groups`.`user_id` = `auth_user`.`id` >>> ) >>> )""", (group_name,), output_field=BooleanField()) >>> >>> Now you can use this function as follows: >>> >>> User.objects.all().annotate(is_customer=build_has_group_raw_sql( >>> 'customer')) >>> >>> >>> On Friday, July 22, 2016 at 7:01:08 PM UTC+3, mishbah wrote: >>>> >>>> Given that I have a django model that has a ForeignKey that is linked >>>> to itself. >>>> >>>> class DjangoModel(): >>>> >>>> [...] >>>> >>>> successor = models.ForeignKey('self', null=True) >>>> >>>> I was able to write a custom django database function like this: >>>> >>>> from django.db.models import BooleanField >>>> from django.db.models import Func >>>> >>>> >>>> class IsNull(Func): >>>> """ >>>> See docs: >>>> https://docs.djangoproject.com/en/1.8/ref/models/database-functions/ >>>> """ >>>> template = '%(expressions)s IS NULL' >>>> >>>> def __init__(self, *args, **kwargs): >>>> kwargs['output_field'] = BooleanField() >>>> super(IsNull, self).__init__(*args, **kwargs) >>>> >>>> So I can do this: >>>> >>>> queryset = DjangoModel.objects.all() >>>> queryset = queryset.annotate(**{'is_latest': IsNull('successor')}) >>>> >>>> and if use `queryset.values()` .. I get >>>> >>>> [{'pk': 1, is_latest': True}, {'pk': 2, 'is_latest': False}, ] >>>> >>>> where `is_latest == True` when `successor` field is NULL for an object. >>>> >>>> Now I want to do something similar, but have no idea where to start! >>>> >>>> The bundled `django.contrib.auth.models.User` has a ManyToMany >>>> relations to `django.contrib.auth.models.Group` model >>>> >>>> For my project, there are multiple user group types, e.g customer / >>>> marketing / finance etc >>>> >>>> What I want to do.. is annotate a `User` queryset with `is_FOO` field >>>> where `FOO` is a group name. e.g `is_customer` or `is_marketing` >>>> >>>> So if I use `.values()` on a queryset, I should get something like this: >>>> >>>> [{'pk': 1, 'is_customer': True, 'is_marketing': False }, {'pk': 1, >>>> 'is_customer': True, 'is_marketing': True }] >>>> >>>> The group name could be hardcoded, e.g >>>> >>>> queryset.annotate(**{'is_customer': IsGroupMember('customer')}) >>>> >>>> I just need help with the `IsGroupMember` database function! >>>> >>>> Is that even possible? Any hints or tips to get me started? >>>> >>>> Any help will be genuinely appreciated. Many Thanks >>>> >>> -- You received this message because you are subscribed to the Google Groups "Django users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/django-users. To view this discussion on the web visit https://groups.google.com/d/msgid/django-users/7c05e64d-6d00-4bdc-8d8e-c9dbf340e38c%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
