问题
I'm developing a mobile application backend with Django 1.9.1 I implemented the follower model and now I want to list all of the followers of a user but I'm currently stuck to do that. I also use Django Rest Framework.
This is my UserProfile model
class UserProfile(models.Model):
# Linking UserProfile to User model.
user = models.OneToOneField(User)
city = models.CharField(null=True, max_length=30, blank=True)
gender = models.CharField(null=True, max_length=10, blank=True) # m for male, f for female
# TODO: Fix the picture later.
# picture = models.ImageField(upload_to='profile_images', blank=True)
age = models.IntegerField(null=True, blank=True)
caption = models.CharField(null=True, max_length=40, blank=True)
following_count = models.IntegerField(default=0)
follower_count = models.IntegerField(default=0)
post_count = models.IntegerField(default=0)
like_count = models.IntegerField(default=0)
date = models.DateTimeField(default=datetime.now(), blank=True)
is_protected = models.BooleanField(default=False)
is_facebook_created_user = models.BooleanField(default=False)
facebook_id = models.CharField(default='', blank=True, max_length=350)
picture_url = models.URLField(blank=True, max_length=100, null=True)
followings = models.ManyToManyField('self', related_name='following', symmetrical=False)
followers = models.ManyToManyField('self', related_name='follower', symmetrical=False)
blocking = models.ManyToManyField('self', related_name='block', symmetrical=False)
blocked_by = models.ManyToManyField('self', related_name='blocked', symmetrical=False)
def block_user(self,username):
other = UserProfile.objects.get(user__username=username)
if not self.is_blocking(username):
self.blocking.add(other)
other.blocked_by.add(self)
return True
else:
return False
def unblock_user(self, username):
other = UserProfile.objects.get(user__username=username)
if self.is_blocking(username):
self.blocking.remove(other)
other.blocked_by.remove(self)
return True
else:
return False
def follow_user(self, username):
other = UserProfile.objects.get(user__username=username)
if not self.is_following(username):
self.followings.add(other)
self.following_count = self.followings.all().count()
self.save()
other.followers.add(self)
other.follower_count = other.followers.all().count()
other.save()
return True
else:
return False
def unfollow_user(self, username):
other = UserProfile.objects.get(user__username=username)
if self.is_following(username):
self.followings.remove(other)
self.following_count = self.followings.all().count()
self.save()
other.followers.remove(self)
other.follower_count = other.followers.all().count()
other.save()
return True
else:
return False
def is_blocking(self,username):
return self.blockings.all().filter(user__username=username).exists()
def is_blocked_by(self,username):
return self.blocked_by.all().filter(user__username=username).exists()
def is_following(self, username): #returns Bool
return self.followings.all().filter(user__username=username).exists()
def is_followed_by(self, username): #returns Bool
return self.followers.all().filter(user__username=username).exists()
def __unicode__(self):
return self.user.username
def get_token(self):
try:
token = Token.objects.get(user_id=self.user_id)
except:
token = 'error'
return token
def get_username(self):
return self.user.username
As you see, I user ManyToManyField for followers. Now I want to list followers of a user but I don't want to list just all of their information since it's unnecessary. I just want to list their usernames because no need for whole information and it's just a waste.
Here is my followers view.
@api_view(['GET'])
def get_followers(request):
username = request.query_params.get('username', None)
if username is not None:
if UserProfile.objects.all().filter(user__username=username).exists():
wanted = UserProfile.objects.get(user__username=username)
followers = wanted.followers.all()
serializer = FollowerSerializer(followers)
return JsonResponse(serializer.data)
else:
return JsonResponse({"result": "user_does_not_exist"})
else:
#TODO: return current user's followers
return JsonResponse({"result": "provide_username"})
Also I added a serializer for only followers of user.
class FollowerSerializer(serializers.ModelSerializer):
class Meta:
model = UserProfile
field = ('followers',)
The problem is, it just lists the all of the user information and it doesn't give usernames but it only lists their id's which i can't do anything.
I forgot to mention that I did think of using ListAPIView but I can't get the username parameter with that. If there is a way of getting the parameter, I could also use ListAPIView for followers.
How can I fix this problem and list only their usernames? Any help will be appreciated.
回答1:
I think what you need is the nested serializer:
class FollowerSerializer(serializers.ModelSerializer):
username = serializers.CharField(source='user__username')
class Meta:
model = UserProfile
fields = ('username', )
class FollowerSerializer(serializers.ModelSerializer):
followers = FollowerSerializer(many=True, read_only=True)
class Meta:
model = UserProfile
fields = ('followers', )
回答2:
I used nested relationships in this link. Django Rest Framework Nested Relationships
Added a new serializer for only username of the user and also changed the other serializer.
# serializes only usernames of users
class EachUserSerializer(serializers.ModelSerializer):
username = serializers.CharField(source='user.username')
class Meta:
model = UserProfile
fields = ('username',)
class FollowerSerializer(serializers.ModelSerializer):
followers = EachUserSerializer(many=True, read_only= True)
followings = EachUserSerializer(many=True,read_only=True)
class Meta:
model = UserProfile
fields = ('followers','followings')
Output was just what was I looking for:
{
"followers": [],
"followings": [
{
"username": "sneijder"
},
{
"username": "drogba"
}
]
}Thank you for your help anyway :)
来源：https://stackoverflow.com/questions/34925690/django-how-to-serialize-from-manytomanyfield-and-list-all