Getting the many-to-many fields of a many-to-many object

问题

If I have the user-group relation as a ManyToMany relationship, and a group-team relation as a ManyToMany relationship, how would I find the user-team relation as a query object?

For example if I had a models.py like this:

class Group(models.Model):
    name = CharField(max_length=100)


class User(models.Model):
    username = models.CharField(max_length=100)
    groups = models.ManyToManyField(Group, blank=True)


class Team(models.Model):
    teamname = models.CharField(max_length=100)
    groups = models.ManyToManyField(Group, blank=True)

I know I can do it by creating a for loop like follows, but it would be much more useful given django's architecture to have it as a query object.

My ugly solution:

user = User.objects.get(username="Ed")
users_teams = []
user_groups = Group.objects.filter(user=user)
for group in user_groups:
    group_teams = Team.objects.filter(group=group)
    for team in group_teams:
        user_teams.append(team)

So this would give me a list query objects that I could associate with a user, but it isn't as easy to use as a single query set the contains query objects for each user-team relation.

I would prefer something that looks like this:

User.objects.get(username="Ed").groups.team_set.objects.all()

which definitely doesn't work. Any ideas?

回答1:

Team.objects.filter(groups__user__username="Ed")

which generates you:

SELECT
  `api_team`.`id`,
  `api_team`.`teamname`
FROM `api_team`
  INNER JOIN `api_team_groups` ON (`api_team`.`id` = `api_team_groups`.`team_id`)
  INNER JOIN `api_group` ON (`api_team_groups`.`group_id` = `api_group`.`id`)
  INNER JOIN `api_user_groups` ON (`api_group`.`id` = `api_user_groups`.`group_id`)
  INNER JOIN `api_user` ON (`api_user_groups`.`user_id` = `api_user`.`id`)
WHERE `api_user`.`username` = 'ed'

来源：https://stackoverflow.com/questions/44980322/getting-the-many-to-many-fields-of-a-many-to-many-object