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Serialize ManyToManyFields with a Through Model in Django REST Framework

I have this M2M relation with through model as
class Person(models.Model):
name = models.CharField(max_length=128)
def __str__(self):
return self.name
class Group(models.Model):
name = models.CharField(max_length=128)
members = models.ManyToManyField(Person, through='Membership')
def __str__(self):
return self.name
class Membership(models.Model):
person = models.ForeignKey(Person, on_delete=models.CASCADE)
group = models.ForeignKey(Group, on_delete=models.CASCADE)
date_joined = models.DateField()
invite_reason = models.CharField(max_length=64)
Please note that, I have extra fields date_joined and invite_reason in the through model.
Now, I want to serialize the Group queryset using DRF and thus I choose the below serializer setup.
class PersonSerializer(serializers.ModelSerializer):
class Meta:
model = Person
fields = "__all__"
class GroupSerializer(serializers.ModelSerializer):
members = PersonSerializer(read_only=True, many=True)
class Meta:
model = Group
fields = "__all__"
and it is returning the following response,
[
{
"id": 1,
"members": [
{
"id": 1,
"name": "Jerin"
}
],
"name": "Developer"
},
{
"id": 2,
"members": [
{
"id": 1,
"name": "Jerin"
}
],
"name": "Team Lead"
}
]
Here, the members field returning the Person information, which is perfect.
But,
How can I add the date_joined and invite_reason field/info into the members field of the JSON response?

class PersonSerializer(serializers.ModelSerializer):
class Meta:
model = Person
fields = "__all__"
def serialize_membership(self, person_instance):
# simple method to serialize the through model fields
membership_instance = person_instance \
.membership_set \
.filter(group=self.context["group_instance"]) \
.first()
if membership_instance:
return MembershipSerializer(membership_instance).data
return {}
def to_representation(self, instance):
rep = super().to_representation(instance)
return {**rep, **self.serialize_membership(instance)}
class MembershipSerializer(serializers.ModelSerializer): # create new serializer to serialize the through model fields
class Meta:
model = Membership
fields = ("date_joined", "invite_reason")
class GroupSerializer(serializers.ModelSerializer):
members = serializers.SerializerMethodField() # use `SerializerMethodField`, can be used to pass context data
def get_members(self, group):
return PersonSerializer(
group.members.all(),
many=True,
context={"group_instance": group} # should pass this `group` instance as context variable for filtering
).data
class Meta:
model = Group
fields = "__all__"
Notes:
Override the to_representation(...) method of PersonSerializer to inject extra data into the members field of the JSON
We need person instance/pk and group instance/pk to identify the Membership instance to be serialized. For that, we have used the serializer context to pass essential data

Use A Serializer Class Inside Other One In Django

I want to have a serializers that use two model at once (If it possible)
models.py
class Club(models.Model):
id = models.AutoField(primary_key=True)
clubname = models.CharField(max_length=50, blank=True, null=True)
location = models.CharField(max_length=50, blank=True, null=True)
scores = models.IntegerField(blank=True, null=True)
serializers.py
class ShowAllClubSerializer(serializers.ModelSerializer):
class Meta:
model = Club
fields
class ShowClubPictures(serializers.ModelSerializer):
class Meta:
model = Clubpictures
fields = ['picture']
views.py
#api_view(["GET", ])
#permission_classes((IsAuthenticated, ))
def show_all_clubs_view(request):
if request.method == "GET":
clubs = Club.objects.all()
if clubs:
for club in clubs:
pictures = Clubpictures.objects.filter(clubid=club.id)
serializer1 = ShowAllClubSerializer(club)
serializer2 = ShowClubPictures(pictures[0])
return Response(serializer1.data, status=status.HTTP_200_OK)
# return Response(serializer2.data, status=status.HTTP_200_OK)
else:
return Response(status=status.HTTP_400_BAD_REQUEST)
Now I Have These In serializers1 and serializers2 Separately:
{
"clubname": "Club Name",
"location": "Somewhere",
"scores": 5,
}
{
"picture": "/media/images/Screenshot.png"
}
How can I take something like this in result:
{
"clubname": "Club Name",
"location": "Somewhere",
"scores": 5,
"picture": "/media/images/Screenshot.png"
}

You can use nested serializers to achieve that.
Your ClubSerializer would look something like this:
class ClubSerializer(serializers.ModelSerializer):
pictures = ClubPictureSerializer(many=True)
class Meta:
model = Club
fields = ('clubname', 'location', 'scores', 'pictures')
class ClubPictures(serializers.ModelSerializer):
class Meta:
model = Clubpictures
fields = ['picture']
assuming you have a ForeignKey from the ClubPicture to your Club with a related_name of pictures.
Also, on your view, you don't need to loop through Club.objects.all() and serialize each object individually - ModelSerializer/Serializer accept a many=True parameters that handles multiple objects already.

How to create object within nested serializer on API create call

I have an API with nested serializers where I overwrote the create method. My nested serializer has Foreign Keys to another model. Now I want to create objects of this other model in the same API call. This is where I am stuck.
My data looks like so:
[
{
"project": "project1",
"name": "Graph1",
"description": "testdescription",
"nodes": [
{
"id": 16,
"name": "target1",
"graph": 49
},
{
"id": 15,
"name": "Node1",
"graph": 49
}
],
"edges": [
{
"id": 14,
"name": "Edge1",
"graph": 49,
"source": 15,
"target": 16
}
]
}
]
The fields source and target are Foreign Keys to the model Node.
Now, I can send this data without a problem when the fields source and target are already existent in the database.
But what I want is, that I send the data and I create a new Node object (source) and a new Node object (target) in the same call.
So far I overwrote the create method to enable nested serialization like so:
class GraphSerializer(serializers.ModelSerializer):
nodes = NodeSerializer(many=True)
edges = EdgeSerializer(many=True)
class Meta:
model = Graph
fields = ('project',
'name',
'description',
'nodes',
'edges',
)
def create(self, validated_data):
nodes_data = validated_data.pop('nodes')
edges_data = validated_data.pop('edges')
graph = Graph.objects.create(**validated_data)
for node_data in nodes_data:
Node.objects.create(graph=graph,**node_data)
for edge_data in edges_data:
Edge.objects.create(graph=graph, **edge_data)
return graph
that works, but like I said I need to create the node objects within the edges with the same call. Is there any way to do this? I can't find any sources online on how to do this.
Any help is very very much appreciated! Thanks so much!
My models
class Graph(models.Model):
project = models.ForeignKey(Project, on_delete=models.CASCADE)
name = models.CharField(max_length=120, blank=True)
description = models.CharField(max_length=400, blank=True)
def __str__(self):
return self.name
#property
def nodes(self):
return self.node_set.all()
#property
def edges(self):
return self.edge_set.all()
class Node(models.Model):
name = models.CharField(max_length=120, blank=True)
graph = models.ForeignKey(Graph, on_delete=models.CASCADE)
def __str__(self):
return self.name
class Edge(models.Model):
name = models.CharField(max_length=120, blank=True)
graph = models.ForeignKey(Graph, on_delete=models.CASCADE)
source = models.ForeignKey(Node, on_delete=models.CASCADE, related_name='source_set')
target = models.ForeignKey(Node, on_delete=models.CASCADE, related_name='target_set')
def __str__(self):
return self.name

You can achieve the custom functionality by WritableNestedSerializers. By default nested serializers are used for read-only but in order to support write-operations to a nested serializer field you'll need to create create() and/or update() methods in order to explicitly specify how the child relationships should be saved. So yes it can be done.
class TrackSerializer(serializers.ModelSerializer):
class Meta:
model = Track
fields = ['order', 'title', 'duration']
class AlbumSerializer(serializers.ModelSerializer):
tracks = TrackSerializer(many=True)
class Meta:
model = Album
fields = ['album_name', 'artist', 'tracks']
def create(self, validated_data):
tracks_data = validated_data.pop('tracks')
album = Album.objects.create(**validated_data)
for track_data in tracks_data:
Track.objects.create(album=album, **track_data)
return album
Another way is to use drf-writable-nested package. Here you create the parent serializers and refer them in the serializer where the relation is required. Only the difference is Update/Create methods are defined in the package which you'll have to write by yourself in above method.
For example, for the following model structure:
Models.py
from django.db import models
class Site(models.Model):
url = models.CharField(max_length=100)
class User(models.Model):
username = models.CharField(max_length=100)
class AccessKey(models.Model):
key = models.CharField(max_length=100)
class Profile(models.Model):
sites = models.ManyToManyField(Site)
user = models.OneToOneField(User)
access_key = models.ForeignKey(AccessKey, null=True)
class Avatar(models.Model):
image = models.CharField(max_length=100)
profile = models.ForeignKey(Profile, related_name='avatars')
serializers.py
from rest_framework import serializers
from drf_writable_nested import WritableNestedModelSerializer
class AvatarSerializer(serializers.ModelSerializer):
image = serializers.CharField()
class Meta:
model = Avatar
fields = ('pk', 'image',)
class SiteSerializer(serializers.ModelSerializer):
url = serializers.CharField()
class Meta:
model = Site
fields = ('pk', 'url',)
class AccessKeySerializer(serializers.ModelSerializer):
class Meta:
model = AccessKey
fields = ('pk', 'key',)
class ProfileSerializer(WritableNestedModelSerializer):
# Direct ManyToMany relation
sites = SiteSerializer(many=True)
# Reverse FK relation
avatars = AvatarSerializer(many=True)
# Direct FK relation
access_key = AccessKeySerializer(allow_null=True)
class Meta:
model = Profile
fields = ('pk', 'sites', 'avatars', 'access_key',)
class UserSerializer(WritableNestedModelSerializer):
# Reverse OneToOne relation
profile = ProfileSerializer()
class Meta:
model = User
fields = ('pk', 'profile', 'username',)

How can the foreign field shows the name instead of its id?

In my models.py, there are two model, the AvailableArea has a foreign field refer to AddressRegion:
class AddressRegion(models.Model):
name = models.CharField(max_length=8)
def __str__(self):
return self.name
def __unicode__(self):
return self.name
class AvailableArea(models.Model):
name = models.CharField(max_length=8)
addressregion = models.ForeignKey(AddressRegion, default=1, related_name='availableareas', on_delete=models.CASCADE)
def __str__(self):
return self.name
def __unicode__(self):
return self.name
In the serializers.py, I serialize all the fields:
class AvailableAreaSerializer(ModelSerializer):
"""
region
"""
class Meta:
model = AvailableArea
fields = "__all__"
In the views.py:
class AddressRegionListAPIView(ListAPIView):
serializer_class = AddressRegionSerializer
permission_classes = []
queryset = AddressRegion.objects.all()
The rest framework data is like this:
[
{
"id": 13,
"name": "st-01",
"addressregion": 3
},
{
"id": 14,
"name": "tg-02",
"addressregion": 4
},
{
"id": 15,
"name": "sx-01",
"addressregion": 3
}
]
I want the addressregion not shows the addressregion's id, but shows the addressregion's name.

You can do the following:
class AvailableAreaSerializer(ModelSerializer):
addressregion_name= serializers.ReadOnlyField(source='addressregion.name')
class Meta:
model = AvailableArea
fields = ('id', 'name', 'addressregion_name')

just add the following code in your serializer:
addressregion_name = serializers.StringRelatedField()
#should be like the following
class AvailableAreaSerializer(ModelSerializer):
addressregion_name = serializers.StringRelatedField()
class Meta:
model = AvailableArea
fields = ('id', 'name', 'addressregion__name')

Your serializer should be like this:
class AvailableAreaSerializer(ModelSerializer):
"""
可用地区
"""
class Meta:
model = AvailableArea
fields = ('id', 'name', 'addressregion__name')
and queryset in View should be:
queryset = AddressRegion.objects.all().select_related('addressregion')
select_related will fetch the result by joining both the table. For more info read this

Django Rest Framework, Relations POST option name

would like to know how to display the Album's name instead of "Album Object" in the POST Tracks' album 'option', refer to below image.
http://s27.postimg.org/8n2uakd9f/Screen_Shot_2014_12_29_at_6_29_07_PM.png
Here is my Model and serializer..
models.py
class Album(models.Model):
name = models.CharField(max_length=100)
artist = models.CharField(max_length=100)
year = models.CharField(max_length=4)
origin = models.CharField(max_length=50)
class Track(models.Model):
album = models.ForeignKey(Album, related_name='tracks')
order = models.IntegerField()
title = models.CharField(max_length=100)
duration = models.IntegerField()
class Meta:
unique_together = ('album', 'order')
ordering = ('order',)
def __unicode__(self):
return '%d: %s' % (self.order, self.title)
serializers.py
class TrackSerializer(serializers.ModelSerializer):
class Meta:
model = Track
fields = ('order', 'title', 'duration','album')
class AlbumSerializer(serializers.ModelSerializer):
tracks = TrackSerializer(many=True, read_only=True)
class Meta:
model = Album
fields = ('name', 'artist', 'year', 'origin', 'tracks')
Album Data(Example):
[
{
"name": "Album1",
"artist": "Artist1",
"year": "2012",
"origin": "Somewhere",
"tracks": []
},
{
"name": "Album2",
"artist": "Artist2",
"year": "2014",
"origin": "Somewhere",
"tracks": []
}
]
Thank you in advance

You can custom this label by defining the method __str__ (or __unicode__ in Python 2) in your model:
class Album(models.Model):
name = models.CharField(max_length=100)
artist = models.CharField(max_length=100)
year = models.CharField(max_length=4)
origin = models.CharField(max_length=50)
def __str__(self):
return "%s (by %s)" % (self.name, self.artist)
This function will be used whenever Django will have to print a reference to this object (including in django-rest-framework and the Django admin)

You can use a CustomRelatedField to control how the object is displayed in Django REST Framework without having to change the Model's__str__ or __unicode__ method.
http://www.django-rest-framework.org/api-guide/relations/#custom-relational-fields