Django Rest Framework - Nested Serialization - django

I have listed the models and Serializers below.
Models:
class CustomGroup(Group):
description = models.CharField(max_length=150, null=True, blank=True, verbose_name="Human readable name")
def __str__(self):
return self.description or self.name
class Meta:
db_table = "groups"
class User(AbstractBaseUser, PermissionsMixin):
"""
Custom user model that supports email.
"""
groups = models.ManyToManyField(
CustomGroup,
verbose_name=('groups'),
blank=True,
help_text= (
'The groups this user belongs to. A user will get all permissions '
'granted to each of their groups.'
),
related_name="user_set",
related_query_name="user",
through="UserGroup"
)
email = models.EmailField(max_length=255, unique=True)
is_active = models.BooleanField(default=True)
tenant = models.ForeignKey(
Tenant, on_delete=models.CASCADE, null=True, db_column="tenant_id", blank=True
)
......
objects = UserManager()
USERNAME_FIELD = "email"
# REQUIRED_FIELDS = ["tenant_id"]
class Meta:
db_table = "users"
class UserGroup(models.Model):
user = models.ForeignKey(User,on_delete=models.CASCADE)
group = models.ForeignKey(CustomGroup, on_delete=models.CASCADE)
tenant = models.ForeignKey(Tenant, on_delete=models.CASCADE, null=True)
class Meta:
db_table = "user_groups"
Serializers:
class UserSerializer(serializers.ModelSerializer):
class Meta:
model = get_user_model()
fields = ("first_name","last_name")
class UserGroupSerializer(serializers.ModelSerializer):
users = UserSerializer(many=True,read_only=True)
class Meta:
model = UserGroup
fields = ('group_id','users')
I want response like this :
{
"group_id":
"users": [
{
"first_name": "",
"last_name":""
}
...
]
...
]
}
I am only getting:
[{"group_id":1}, ...}]
How does the UserSerializer serialize the required user ids from the User model? Since user is defined as a foreign key in UserGroup does it happen automatically? or am i missing any relation between User and UserGroup?

Your UserGroup is only linked to one User and one Group. So you will only be able to access to one user and one group directly.
(Didn't you just mispell user in your serializer ? you wrote users)
class UserSerializer(serializers.ModelSerializer):
class Meta:
model = get_user_model()
fields = ("first_name","last_name")
class UserGroupSerializer(serializers.ModelSerializer):
user = UserSerializer(read_only=True)
class Meta:
model = UserGroup
fields = ('group_id','user')
but this will give you something like
{
"group": "<group_pk>",
"user": {
"first_name": "first_name",
"last_name": "last_name"
}
}
If you want to associate a specific Group with all related user, it takes something different. You would need to retrieve all the Users linked to a UserGroup having the group_id of the current UserGroup.
class UserGroupSerializer(serializers.ModelSerializer):
class Meta:
model = UserGroup
fields = ('group_id', )
def to_representation(self, instance):
data = super().to_representation(instance)
related_users = get_user_model().objects.filter(usergroup__group=instance.group)
data['users'] = UserSerializer(instance=related_users, many=true).data
return data
But, again, this may not be the most efficient way to achieve this as it will probably result in duplicated data. So you should probably consider accessing it from your "GroupSerializer". The same logic would be applied.

Related

Django, DRF (& React) Foreign key, how to display the name value instead of the foreign key id

There are two Django models - ClientCompany & Proposal and the foreign key of ClientCompany is within the Proposal model. In Proposal how do I display the name of the ClientCompany instead of the foreign key id?
models.py:
class ClientCompany(models.Model):
name = models.CharField("Client Name", max_length=255)
abn_acn = models.BigIntegerField("ABN / ACN")
def __str__(self):
return self.name
class Proposal(models.Model):
proj_name = models.CharField("Project Name", max_length=255)
loc_state = models.CharField(
max_length=3,
)
proj_type = models.CharField(
max_length=30,
)
prop_status = models.CharField(
max_length=20,
)
client = models.ForeignKey(ClientCompany, on_delete=models.CASCADE)
oneic = models.ForeignKey(
User, on_delete=models.CASCADE, related_name='main_engineer')
twoic = models.ForeignKey(
User, on_delete=models.CASCADE, related_name='second_engineer')
created_at = models.DateTimeField(default=datetime.now)
def __str__(self):
return self.proj_name
serializers.py:
class ClientSerializer(serializers.ModelSerializer):
class Meta:
model = ClientCompany
fields = ('id', 'name', 'abn_acn')
class ProposalSerializer(serializers.ModelSerializer):
class Meta:
model = Proposal
fields = ('id', 'proj_name', 'loc_state', 'proj_type', 'prop_status', 'client', 'oneic', 'twoic',)
queryset api.py:
class ProposalViewSet(viewsets.ModelViewSet):
permission_classes = [permissions.IsAuthenticated, ]
queryset = Proposal.objects.all()
serializer_class = ProposalSerializer
currentlyshows the client foreign key id
I've been stuck on this, tried to apply the existing solutions recommended for similar problems but had no luck... if someone can tell me what I'm missing - thanks
I found this worked in the end by adding the serializers.SlugRelatedField line in serializers.py:
class ProposalSerializer(serializers.ModelSerializer):
client = serializers.SlugRelatedField(slug_field="name", read_only=True)
class Meta:
model = Proposal
fields = ('id', 'proj_name', 'loc_state', 'proj_type', 'prop_status',
'client', 'oneic', 'twoic',)
Update your serializer like this:
class ProposalSerializer(serializers.ModelSerializer):
client = ClientSerializer()
class Meta:
model = Proposal
fields = ('id', 'proj_name', 'loc_state', 'proj_type', 'prop_status', 'client', 'oneic', 'twoic',)

How can I make a writable ManyToManyField with a Through Model in Django Rest Framework?

I have a Product class that has "source products"; I use a many-to-many field with a through model to represent it (the database tables already exist, and that's the only way I found to configure the models):
class Product(models.Model):
uuid = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
product_name = models.TextField()
source_products = models.ManyToManyField('self', symmetrical=False, related_name='derived_products', through='Link', through_fields=('product', 'source'),)
class Meta:
db_table = 'product'
managed = False
class Link(models.Model):
product = models.ForeignKey('Product', models.CASCADE, db_column='uuid', related_name='source_links')
source = models.ForeignKey('Product', models.CASCADE, db_column='source_uuid', related_name='+')
class Meta:
db_table = 'link'
unique_together = (('product', 'source'),)
managed = False
My serializer is dead simple:
class ProductSerializer(serializers.ModelSerializer):
class Meta:
model = Product
fields = ('uuid', 'product_name', 'source_products', )
A GET request returns:
{
"product_name": "dummy.fra",
"source_products": [
"17b021e7-3d6b-4d29-a80b-895d62710080"
],
"uuid": "48c5a344-877e-4e3f-9a4b-2daa136b68fe"
}
The since ManyToManyFields with a Through Model are read-only, how do I go about to create a product including the link between products? I'd like to send a POST request that follows the same format as the GET response (i.e., a source_products field that lists UUIDs of existing products).
You can use PrimaryKeyRelatedField but you have to write custom create method.
class ProductSerializer(serializers.ModelSerializer):
source_products = serializers.PrimaryKeyRelatedField(many=True, queryset=Products.objects.all())
class Meta:
model = Product
fields = ('uuid', 'product_name', 'source_products', )
def create(self, validated_data):
source_products = validated_data.pop('source_products', [])
product = Product.objects.create(**validated_data)
for source in source_products:
product.source_products.add(source)
return product
Your data will be like this
{
"product_name": "dummy.fra",
"source_products": [
"17b021e7-3d6b-4d29-a80b-895d62710080"
],
"uuid": "48c5a344-877e-4e3f-9a4b-2daa136b68fe"
}
The serializer has to override create() and access the unvalidated GET parameters (self.context['request'].data) directly:
class ProductSerializer(serializers.ModelSerializer):
def create(self, validated_data):
# extract sources data
unvalidated_data = self.context['request'].data
sources_data = unvalidated_data.get('source_products', [])
# save objects
instance = Product.objects.create(**validated_data)
for uuid in sources_data:
source = Product.objects.get(pk=uuid)
instance.source_links.create(source=source)
return instance
class Meta:
model = Product
fields = ('uuid', 'product_name', 'source_products', )

Access field from intermediary model in Django Rest Framework

Having a hard time trying to access a field from an intermediary model in DRF.
Let's see the related models:
class School(models.Model):
created = models.DateTimeField(auto_now_add=True)
name = models.CharField(max_length=50, verbose_name=_(u'Name'))
staff_order = models.ManyToManyField(settings.AUTH_USER_MODEL, verbose_name=_(u'Staff ordering'), through='StaffOrder', related_name='school_staff_order')
class User(AbstractUser):
phone = models.CharField(max_length=20, blank=True, null=True)
address = models.CharField(max_length=150, blank=True, null=True)
about_me = models.CharField(max_length=200, blank=True, null=True)
REQUIRED_FIELDS = ['email']
def __unicode__(self):
return u'{0}'.format(self.username)
class StaffOrder(models.Model):
user = models.ForeignKey(settings.AUTH_USER_MODEL)
school = models.ForeignKey(School)
order = models.PositiveSmallIntegerField(default=0, verbose_name=_(u'Staff ordering for this school'))
class Meta:
verbose_name_plural = _(u'Staff ordering')
Now what I'm expecting is being able to read order field from StaffOrder in when returning a QuerySet for users (StaffSerializer). Here are the Serializers:
class StaffRoleSerializer(serializers.ModelSerializer):
class Meta:
model = StaffOrder
fields = (
'order',
)
class StaffSerializer(serializers.ModelSerializer):
username = serializers.CharField(max_length=75, required=True)
email = serializers.CharField(max_length=75, required=True)
order = StaffRoleSerializer(source='school_staff_order')
class Meta:
model = User
What is returned in order for the StaffSerializer is a Manager, instead of the order field from the StaffOrder model related with this User.
A JSON expected response for Staff would be something like this:
[
{
"username": "Denise",
"email": "deniseburton#maximind.com",
"order": 9
},
{
"username": "Ina",
"email": "inaburton#maximind.com",
"order": 4
}
]
I'd love to be able to also write this value from the serializer, but I can do that in the Viewset, but I really need to read this value in the Serializer itself...any idea what I'm missing here?
First you have to understand that one user can have many staff orders. In your models you have defined it that way.
To get the json output you have specified in your question you need to query the StaffOrder objects instead of users.
class StaffOrderSerializer(serializers.ModelSerializer):
username = serializers.CharField(source='user.username')
email = serializers.CharField(source='user.email')
class Meta:
model = StaffOrder
fields = ('order', )
Use this serializer class in a list view:
class StaffOrderListApi(generics.ListAPIView):
serializer_class = StaffOrderSerializer
def get_queryset(self):
# using distinct because same user can have multiple staff orders
# based on your example it seems you want distinct users
return StaffOrder.objects.all().distinct('user')
This will get you exactly the json you want.

Using reverse relationships with django-rest-framework's serializer

My model looks like this:
class User(TimestampedModel):
name = models.CharField(max_length=30, null=False, blank=False)
device = models.CharField(max_length=255, null=False, blank=False)
class Comment(TimestampedModel):
user = models.ForeignKey(User, on_delete=models.PROTECT, blank=True, null=True)
contents = models.CharField(max_length=510)
rating = models.IntegerField(blank=False, null=False)
And my serializer looks like this:
class UserSerializer(serializers.ModelSerializer):
class Meta:
model = User
fields = ('name',)
class CommentListItemSerializer(serializers.ModelSerializer):
user = UserSerializer()
class Meta:
model = Comment
fields = ('user', 'contents', 'rating')
And the view:
class CommentsList(generics.ListAPIView):
serializer_class = CommentListItemSerializer
queryset = Comment.objects.all()
It's almost getting the job done ;). The response I'm getting looks like this:
"results": [
{
"user": {
"name": "Ania"
},
"contents": "Very good",
"rating": 6
},
{
"user": {
"name": "Anuk"
},
"contents": "Not very good",
"rating": 1
}
]
There are two problems with that response.
I don't want to have this nested object "user.name". I'd like to receive that as a simple string field, for example "username".
Serializer makes a database query (not a join, but a separate query) for each user, to get his/her name. Since that's unacceptable, how to fix that?
Serializer makes a database query (not a join, but a separate query)
for each user, to get his/her name.
You can use select_related() on the queryset attribute of your view. Then accessing user.name will not result in further database queries.
class CommentsList(generics.ListAPIView):
serializer_class = CommentListItemSerializer
queryset = Comment.objects.all().select_related('user') # use select_related
I don't want to have this nested object "user.name". I'd like to
receive that as a simple string field, for example "username"
You can define a read-only username field in your serializer with source argument. This will return a username field in response.
class CommentListItemSerializer(serializers.ModelSerializer):
# define read-only username field
username = serializers.CharField(source='user.name', read_only=True)
class Meta:
model = Comment
fields = ('username', 'contents', 'rating')
You can add custom functions as fields
class Comment(models.Model):
user = models.ForeignKey(User, on_delete=models.PROTECT, blank=True, null=True)
contents = models.CharField(max_length=510)
rating = models.IntegerField(blank=False, null=False)
def username(self):
return self.user.name
class CommentListItemSerializer(serializers.ModelSerializer):
class Meta:
model = Comment
fields = ('username', 'contents', 'rating')

How to use a model field for multiple models in Django Rest Framework

I have a model BstUserActionLog with a foreign key to Django model User. I have another model for user profile information, BstUserProfile. When I do serialize BstUserActionLog with ModelSerializer I do have Django User info serialized as it is supposed to be. But I also need to add BstUserProfile serialized using the same user_id used for User model.
How can I serialize BstUserActionLog with model User and BstUserProfile are both serialized?
From my models.py:
class BstUserActionLog(models.Model):
id = models.AutoField(primary_key=True)
user = models.ForeignKey(User)
bst_action_type = models.ForeignKey(BstActionType)
action_date = models.DateTimeField(auto_now_add=True)
bst_book = models.ForeignKey(BstBook)
new_value_id = models.IntegerField(blank=True, null=True)
old_value_id = models.IntegerField(blank=True, null=True)
class Meta:
managed = False
db_table = 'bst_user_action_log'
class BstUserProfile(models.Model):
id = models.AutoField(primary_key=True)
user = models.ForeignKey(User, unique=True)
website = models.CharField(max_length=200)
picture = models.CharField(max_length=100)
is_avatar_uploaded = models.BooleanField(default=False)
is_cover_uploaded = models.BooleanField(default=False)
class Meta:
managed = False
db_table = 'bst_user_profile'
app_label = 'bst'
From my serializers.py:
class UserSerializer(serializers.ModelSerializer):
class Meta:
model = User
fields = ('id','username',)
class BstUserActionLogSerializer(serializers.ModelSerializer):
user = UserSerializer()
class Meta:
model = BstUserActionLog
fields = ('id', 'user', 'bst_action_type', 'action_date', 'bst_book', 'new_value_id', 'old_value_id')
depth = 3
The key to my solution is SerializerMethodField. With this a new field can be added which is calculated with a method. This method signature contains the object to be serialized. After that a regular method serializer is used to return the serialized object.
From my serializers.py
class BstUserProfileSerializer(serializers.ModelSerializer):
class Meta:
model = BstUserProfile
fields = ('is_avatar_uploaded', 'is_cover_uploaded')
class BstUserActionLogSerializer(serializers.ModelSerializer):
user = UserSerializer()
user_profile = serializers.SerializerMethodField()
def get_user_profile(self, obj):
try:
user_profile = BstUserProfile.objects.get(user_id=obj.user_id)
return BstUserProfileSerializer(user_profile).data
except Exception as e:
return {}
class Meta:
model = BstUserActionLog
fields = ('id', 'user', 'user_profile', 'bst_action_type', 'action_date', 'bst_book', 'new_value_id', 'old_value_id')
depth = 3