I know that this question has been asked before, but I've tried so many different solutions and just cannot seem to get it to work. All I am attempting to do is display one object within another on an api call. In this simple example, lets say that I have an artist object and a track object. When I serialize the track object, I would like for the artist object that it refers to using a foreign key to be displayed.
Here is my models.py:
from django.db import models
class Artist(models.Model):
artist_name = models.CharField(max_length=100)
class Track(models.Model):
artist = models.ForeignKey(Artist, on_delete=models.CASCADE, verbose_name='Artist' )
track_name = models.CharField(max_length=100)
and my serializers.py
from rest_framework import serializers
from . import models
class ArtistSerializer(serializers.ModelSerializer):
class Meta:
model = models.Artist
fields = '__all__'
class TrackSerializer(serializers.ModelSerializer):
artist = ArtistSerializer(read_only=True)
class Meta:
model = models.Track
fields = ('id', 'track_name', 'artist')
If anyone could help, it would be greatly appreciated!
Thanks
Related
So basically I have a django model that has a ManyToManyField of friends and two methods that run on it. Here are my files:
Models.py:
from django.db import models
from django.contrib.auth.models import User
class Profile(models.Model):
first_name = models.CharField(max_length=50, blank=True)
last_name = models.CharField(max_length=50, blank=True)
user = models.OneToOneField(User, on_delete=models.CASCADE)
friends = models.ManyToManyField(User, blank=True, related_name='friends')
def friends_list(self):
return self.friends.all()
def number_of_friends(self):
return self.friends.all().count()
Serialzers.py:
from rest_framework import serializers
from .models import Profile
class ProfileSerializer(serializers.ModelSerializer):
class Meta:
model = Profile
fields = '__all__'
Views.py:
from rest_framework import viewsets, permissions
from .models import Profile
from .serializers import ProfileSerializer
class ProfileViewSet(viewsets.ModelViewSet):
queryset = Profile.objects.all()
permission_classes = [
permissions.AllowAny
]
serializer_class = ProfileSerializer
The issue is that in the Api, the return values of the method aren't there. The friends_list method for example is supposed to return a list of friends you have and even though this does work in a traditional django project, the Django Rest Framework is not showing any value for this method. How can I fix this and get the return values for both methods to show up in the api?
Since the model serializer picks up only model fields for the serializer fields, you won't automatically get any methods copied over.
You can still send this read only data over the API by explicitly adding the two fields with reference to the model methods
class ProfileSerializer(serializers.ModelSerializer):
class Meta:
model = Profile
fields = [
# need to explicitly define all fields I believe
'friends_list',
'number_of_friends',
]
Now that the two fields (matching the method name are declared, DRF should create SerializerMethodField or ReadOnly field (not sure which one, but they are similar) for each of them.
It works coz it sets the source for those fields to be the same name, and if finds some attribute (in this case the methods) on the model.
If that doesn't work, you can
class ProfileSerializer(serializers.ModelSerializer):
friends_list = serializers.SerializerMethodField()
number_of_friends = serializers.SerializerMethodField()
class Meta:
model = Profile
fields = [
# need to explicitly define all fields I believe
'friends_list',
'number_of_friends',
]
def get_friends_list(self, instance):
return instance.friends_list()
def get_number_of_friends(self, instance):
return instance.number_of_friends()
when you use __all__ it call fields only you have to call fields with methods using list like that
`fileds = ["first_name","last_name","user",
"friends","friends_list","number_of_friends"
]`
I have 2 models that look like this:
models.py
class Client(models.Model):
deal = models.ManyToManyField('Deal', related_name="clients")
class Deal(models.Model):
client = models.ManyToManyField(Client, related_name="deals")
Then in the admin, I have inlined the related models to make it easy to make changes regardless of the object type you have open.
admin.py
class ClientInline(admin.TabularInline):
model = Deal.client.through
class DealAdmin(admin.ModelAdmin):
inlines = [ClientInline]
class DealInline(admin.TabularInline):
model = Client.deal.through
class ClientAdmin(admin.ModelAdmin):
inlines = [DealInline]
However, if you add a Client to a Deal and then open the Client detail page, the corresponding deal does not appear. Is there something I'm not connecting?
It is enough to have relation define only in one model. Otherwise you'll have 2 separate tables for separate ManyToMany relation: ClientDeal and DealClient.
What you need to do is to choose which one you need to leave. And probably update Admin inlines according to Django Admin documentation
class Client(models.Model):
deals = models.ManyToManyField('Deal', related_name="clients")
class Deal(models.Model):
pass
Yes, If you're using models.manytoMany() , you have to put it only in one model. no the two
But there's a very good attribute you should use: through
with through attribute you can create a intermediate model. here there's an example:
from django.db import models
class Person(models.Model):
name = models.CharField(max_length=200)
groups = models.ManyToManyField('Group', through='GroupMember', related_name='people')
class Meta:
ordering = ['name']
def __unicode__(self):
return self.name
class Group(models.Model):
name = models.CharField(max_length=200)
class Meta:
ordering = ['name']
def __unicode__(self):
return self.name
class GroupMember(models.Model):
person = models.ForeignKey(Person, related_name='membership')
group = models.ForeignKey(Group, related_name='membership')
type = models.CharField(max_length=100)
def __unicode__(self):
return "%s is in group %s (as %s)" % (self.person, self.group, self.type))
later, you can use your inline admin class!
I just tested this an you were actually really close.
First, #wowkin2 said, you don't want to define a ManyToManyField in both models so I would probably just define it in your Deal model.
Second, replace this:
class DealInline(admin.TabularInline):
model = Client.deal.through
with this:
class DealInline(admin.TabularInline):
model = Deal.client.through
And everything should work.
So, this is what your files should now look like:
models.py
class Deal(models.Model):
client = models.ManyToManyField(Client, related_name="deals")
admin.py
class ClientInline(admin.TabularInline):
model = Deal.client.through
class DealAdmin(admin.ModelAdmin):
inlines = [ClientInline]
class DealInline(admin.TabularInline):
model = Deal.client.through
class ClientAdmin(admin.ModelAdmin):
inlines = [DealInline]
I have been getting my head around these basics but I am not getting it right. I am trying to associate my view to my user model using team which is a foreign key. When I try to create of a gps, I get an error saying "team is a required field" but instead it should be read only. The team attribute should be filled automatically with the id of the currentUser
Model
class User(models.Model):
first_name = models.CharField(max_length=200,blank=False)
last_name = models.CharField(max_length=200, blank=False)
class Gps(models.Model):
location = models.CharField(max_length=200,blank=False)
team= models.ForeignKey(User, on_delete=models.CASCADE)
serializers
class GpsSerializer(serializers.ModelSerializer):
class Meta:
model = Gps
fields = ('id','location','team')
view
class Gps_list(generics.ListCreateAPIView):
queryset = Gps.objects.all()
serializer_class = GpsSerializer
team = serializers.PrimaryKeyRelatedField(
read_only=True,
default=serializers.CurrentUserDefault()
)
There are two changes needed. First, team field definition should be moved to serializer class instead of view. Second, you should use Django's contrib.auth.User model instead of your definition of User, as because serializers.CurrentUserDefault() will bring request.user only. So you should remove your User definition and import that to your models.py:
from django.contrib.auth.models import User
Further steps would be to replace read_only=True with queryset=User.objects.all() to allow create.
As stated in this question
With Django REST Framework, a standard ModelSerializer will allow ForeignKey model relationships to be assigned or changed by POSTing an ID as an Integer.
I am attempting to update a reverse relationship of the following format:
class Lesson(models.Model):
name = models.TextField()
class Quiz(models.Model):
lesson = models.ForeignKey(Lesson, related_name='quizzes', null=True)
class LessonSerializer(serializers.ModelSerializer):
quizzes = serializers.PrimaryKeyRelatedField(queryset=Quiz.objects.all(), many=True, write_only=True)
class Meta:
model = Lesson
fields = ('quizzes')
When posting an update containing an array of quiz primary keys using LessonSerializer I get TypeError: 'Quiz' instance expected, got '1'.
Is it possible to assign or change a reverse relationship by POSTing an array of primary keys?
You don't need special field in a serializer, DRF serializers is smart enough to figure out related field from a fields value.
class LessonSerializer(serializers.ModelSerializer):
class Meta:
model = Lesson
fields = ('quizzes', 'name')
And you should pass list of ids, if there is only one value it should be a list anyway.
To solve this you need to create a Quiz instance first before you assign it to Lesson. Below's a small change to your code.
class Lesson(models.Model):
name = models.TextField()
class Quiz(models.Model):
lesson = models.ForeignKey(Lesson, related_name='quizzes', null=True)
class LessonSerializer(serializers.ModelSerializer):
quizzes = serializers.PrimaryKeyRelatedField(queryset=Quiz.objects.all(), many=True, write_only=True)
class Meta:
model = Lesson
fields = ('quizzes')
class QuizSerializer(serializers.ModelSerializer):
class Meta:
model = Quiz
fields = ('name')
Create POST request with with quiz then run your post again
models.py:
class Station(models.Model):
station = models.CharField()
class Flat(models.Model):
station = models.ForeignKey(Station, related_name="metro")
# another fields
Then in serializers.py:
class StationSerializer(serializers.ModelSerializer):
station = serializers.RelatedField(read_only=True)
class Meta:
model = Station
class FlatSerializer(serializers.ModelSerializer):
station_name = serializers.RelatedField(source='station', read_only=True)
class Meta:
model = Flat
fields = ('station_name',)
And I have an error:
NotImplementedError: RelatedField.to_representation() must be implemented.
If you are upgrading from REST framework version 2 you might want ReadOnlyField.
I read this, but it does not help me.
How to fix that?
Thanks!
RelatedField is the base class for all fields which work on relations. Usually you should not use it unless you are subclassing it for a custom field.
In your case, you don't even need a related field at all. You are only looking for a read-only single foreign key representation, so you can just use a CharField.
class StationSerializer(serializers.ModelSerializer):
station = serializers.CharField(read_only=True)
class Meta:
model = Station
class FlatSerializer(serializers.ModelSerializer):
station_name = serializers.CharField(source='station.name', read_only=True)
class Meta:
model = Flat
fields = ('station_name', )
You also appear to want the name of the Station object in your FlatSerializer. You should have the source point to the exact field, so I updated it to station.name for you.