I have nested models and many to many relations. When I try to serialize them, results are not visible.
Tried everything in documentation and related names etc.
My base model is like this:
class Question(models.Model):
ques_code = models.CharField(max_length=12, null=True, default='Ques Code')
def __str__(self):
return self.ques_code
Child Model is:
class MCQuestion(Question):
answer_order = models.CharField(
max_length=30, null=True, blank=True,
choices=ANSWER_ORDER_OPTIONS,
help_text=_("The order in which multichoice "
"answer options are displayed "
"to the user"),
verbose_name=_("Answer Order"))
Then linked answer class with key as:
class Answer(models.Model):
mcquestion = models.ForeignKey(MCQuestion,related_name='answers', on_delete=models.CASCADE)
content = models.CharField(max_length=1000,
blank=False,
help_text=_("Enter the answer text that "
"you want displayed"),
verbose_name=_("Content"))
correct = models.BooleanField(blank=False,
default=False,
help_text=_("Is this a correct answer?"),
verbose_name=_("Correct"))
def __str__(self):
return self.content
Serializers are as:
class AnswerSerializer(serializers.ModelSerializer):
class Meta:
model = Answer
fields = ('content','correct')
class MCQuestionSerializer(serializers.ModelSerializer):
answers = AnswerSerializer(many=True, read_only=True)
#answers = serializers.SerializerMethodField()
quiz = QuizSerializer(many=True)
class Meta:
model = MCQuestion
fields = ('ques_code','answers')
Views are:
class QuestionViewSet(viewsets.ModelViewSet):
queryset = Question.objects.all()
serializer_class = MCQuestionSerializer
When I access API for questions, nested answers are not visible. I checked all documentation and checked and changed my code.
If I try using answers = serializers.SerializerMethodField() and define get_answers function for it, error comes saying "Question has no attribute of answers"
I think it is due to child and mother model system. It is searching attribute in Question, not in MCQuestion model. What can I do?
You were using the "wrong queryset-serializer combination" for the viewset class.
So, change the queryset reference in your view class as ,
class QuestionViewSet(viewsets.ModelViewSet):
queryset = MCQuestion.objects.all()
serializer_class = MCQuestionSerializer
Apart from that, I'm not sure you are aware of Django Model Inheritance. Anyway read it from here if necessary, Django Model Inheriitance
Related
The problem is I have a 'details' field which should render into a nested relationship with it's parent serializer. I have tried a bunch of stuff and nothing seems to be working.
Here's my models:
class BusinessOrderModel(OrderToModel):
reference = models.IntegerField()
business_num = models.ForeignKey('BusinessModel', on_delete=models.CASCADE)
def __str__(self):
return str(self.reference)
class BusinessModel(models.Model):
Business_num = models.IntegerField(primary_key=True)
def __str__(self):
return str(self.Business_num)
class DetailModel(models.Model):
id = models.AutoField(primary_key=True)
detail = models.TextField()
order = models.ForeignKey('BusinessOrderModel', on_delete=models.CASCADE)
and here's my serializers which aren't working:
class DetailSerializer(serializers.ModelSerializer):
class Meta:
model = DetailModel
fields = ('id', 'detail')
class BusinessOrderSerializer(serializers.ModelSerializer):
details = DetailSerializer(many=True)
class Meta:
model = BusinessOrderModel
fields = ('reference', 'business_num', 'details')
I've tried many different things but I get this error:
Got AttributeError when attempting to get a value for field details
on serializer BusinessOrderSerializer. The serializer field might be
named incorrectly and not match any attribute or key on the
BusinessOrderModel instance. Original exception text was:
'BusinessOrderModel' object has no attribute 'details'.
Any help is much appreciated.
Thank you very much.
Using details to lookup reverse relationships only works if you set it as the related_name. The default for BusinessOrderModel to DetailModel will be detailmodel_set.
To make it accessible by calling details you should make this change:
class DetailModel(models.Model):
id = models.AutoField(primary_key=True)
detail = models.TextField()
order = models.ForeignKey('BusinessOrderModel', related_name="details", on_delete=models.CASCADE)
Now you can use DetailModel.objects.get(id=1).details.all()
You can also customize the query in your serializer:
class BusinessOrderSerializer(serializers.ModelSerializer):
details = SerializerMethodField()
class Meta:
model = BusinessOrderModel
fields = ('reference', 'business_num', 'details')
def get_details(self, obj):
return DetailSerializer(obj.details.filter(), many=True).data
models.py
class Product(models.Model):
title = models.CharField(max_length=200)
description = models.TextField()
price = models.DecimalField(decimal_places=5,max_digits= 1500)
summary = models.TextField()
featured = models.BooleanField()
def __str__(self):
return self.title
# return f'product title:{self.title}-product price:{self.price}'workok
class Meta:
ordering = ('-price',)
class Opinion(models.Model):
name = models.CharField(max_length=20)
email = models.EmailField(max_length=20)
body = models.TextField()
opinion_date = models.DateTimeField(auto_now_add=True)
active = models.BooleanField(default=False)
product = models.ForeignKey(Product, on_delete=models.CASCADE, related_name='opinion_set')
def __str__(self):
return f'({self.name}) add opinion about ({self.product})'
forms.py:
from django.forms import ModelForm
from .models import Product #space after from keyword
class OpinionModelForm(ModelForm):
class Meta:
model = Product
fields = ['name','email','body','product']
invalid in code line :
fields = ['name','email','body','product'] #---- NOT WORK !!!
, but if i change above code to :
fields = "__all__" # ----it is WORKing ok without any problem !!
question : what is the error? I am not need all the fields in the Product model (like active boolean field), I need only 'name','email','body','product' fields .
According to the error and the code you provided the main problem is that you made a mistake in chosing model in serializer:
class OpinionModelForm(ModelForm):
class Meta:
model = Product
fields = ['name','email','body','product']
Serializer name is OpinionModelForm and listed fields belong to Opinion so I guess you actually wanted to serialize Opinion and no Product as you defined at this line:
model = Product
Simply change it to:
model = Opinion
I have the following three models structured around the premise of the Survey.
class Survey(models.Model):
...
id = models.UUIDField(_('Id'), primary_key=True, default=uuid.uuid4, editable=False,)
name = models.CharField(_('Name'), max_length=120, blank=True, unique=True)
slug = models.SlugField(_('Slug'), max_length=120, blank=True, unique=True)
description = models.TextField(_('Description'), blank=True)
...
Each Survey can have multiple questions SurveyQuestion:
class SurveyQuestion(models.Model):
...
survey = models.ForeignKey('surveys.Survey', on_delete=models.CASCADE, null=True, blank=True,)
And each SurveyQuestion can have multiple answers SurveyQuestionAnswer:
class SurveyQuestionAnswer(models.Model):
...
survey_question = models.ForeignKey('surveys.SurveyQuestion', on_delete=models.CASCADE, null=True, blank=True,)
For the sake of brevity, imagine my Survey serializers as being as simple as possible:
class SurveySerialializer(serializers.ModelSerializer):
class Meta:
model = Survey
fields = ('__all__')
Effectively, what I have is the following:
class Survey(APIView):
"""
Survey GET request endpoint: fetches Survey
"""
permission_classes = User
def get(self, request, survey_slug):
survey = Survey.objects.get(slug=survey_slug)
serializer = SurveySerializer(survey)
response = get_hug_response(message='Organisation Active Survey Fetched Successfully', data=serializer.data)
return Response(data=response, status=status.HTTP_200_OK)
But, as you could all probably tell, the corresponding surveys.get('slug') fetch only returns the fields in the Survey model. Ideally, I would like to have some sort of fetch for each SurveyQuestion, and within that nested the SurveyQuestionAnswers
Any pro-tips and pointers would be most appreciated.
I have tried a few things, that only throw errors. I'm struggling to know what this type of API relationship is called in DRF so I can't find appropriate example guides to base the same principles from...
Relevant versions:
Django==2.2.1
djangorestframework==3.9.3
Create two serializers, SurveyQuestionAnswerSerializer and SurveyQuestionSerializer
class SurveyQuestionAnswerSerializer(serializers.ModelSerializer):
class Meta:
model = SurveyQuestionAnswer
fields = '__all__'
class SurveyQuestionSerializer(serializers.ModelSerializer):
survey_questionanswers = SurveyQuestionAnswerSerializer(many=True, read_only=True, source="surveyquestionanswer_set")
class Meta:
model = SurveyQuestion
fields = '__all__'
class SurveySerializer(serializers.ModelSerializer):
survey_questions = SurveyQuestionSerializer(many=True, read_only=True, source="surveyquestion_set")
class Meta:
model = Survey
fields = '__all__'
For more info,
1. What is related_name used for in Django?
2. DRF Serializer's source argument
I am trying to create a Many-To-Many relationship between two models- Author and Book. My use-case is that I should be able to add a new book to the database with an author that already exists in the database.
models.py
class Author(models.Model):
author_id = models.CharField(max_length=20, primary_key=True)
name = models.CharField(blank=True, null=True)
def __unicode__(self):
return self.name
class Meta:
ordering = ('author_id',)
class Book(models.Model):
title = models.CharField(max_length=50, primary_key=True)
authors = models.ManyToManyField(Author)
def __unicode__(self):
return self.title
class Meta:
ordering = ('title',)
serializers.py
class AuthorSerializer(serializers.ModelSerializer):
class Meta:
model = Author
fields = ('author_id', 'name')
class BookSerializer(serializers.ModelSerializer):
authors = AuthorSerializer(many=True)
class Meta:
model = Book
fields = ('title', 'authors')
def create(self, validated_data):
book = Book.objects.create(name=validated_data['title'])
for item in validated_data['authors']:
author = Author.objects.get(author_id=item['author_id'])
book.authors.add(author)
return book
Let's say my Author table already has an Author:
1, George RR Martin
Now if I want to add a new book with an existing author, this is the request I send using httpie:
http -j POST http://localhost/books title="The Winds of Winter" authors:='[{"author_id":"1"}]'
and when I do, I get this error:
Output Error
{
"authors": [
{
"author_id": [
"This field must be unique."
]
}
]
}
It seems like the AuthorSerializer is being called which checks the provided author_id against the ones in the database already and throws this error.
Any help on this would be appreciated.
Is there a specific reason you have to use a custom PK field?
Django automatically creates primary key fields for you. If you simply delete that field from your model and your serializer (and create/run a migration on your database), you won't have to specify the pk in your POST call from your frontend, and Django will create an AutoField that auto-increments your model's id:
class Author(models.Model):
# Remove this line and run makemigrations.
# author_id = models.CharField(max_length=20, primary_key=True)
name = models.CharField(blank=True, null=True)
def __unicode__(self):
return self.name
class Meta:
ordering = ('author_id',)
If not, consider using an models.AutoField rather than models.CharField for your primary key field, and again, don't include this in your POST call.
Note, that if you already have a big database created, you might have to do some intricate work in your migration, a la this answer:
I'm building a serializer in django using the django rest framework. I need to filter the query set for a nested model.
I found How do you filter a nested serializer in Django Rest Framework?, which seemed to have the answer, but when I implemented it there was no change in my data. The only difference I can see is that the serializer referencing the filtered list serializer has other fields as well.
The models (abbreviated for clarity):
class GCUser(models.Model):
first_name = models.CharField(max_length=50)
last_name = models.CharField(max_length=50)
email = models.EmailField()
is_member = models.BooleanField(default=False)
age = models.SmallIntegerField(blank=True, null=True)
session_key = models.CharField(max_length=100, db_index=True, blank=True, null=True)
class Connection(models.Model):
creation_date = models.DateTimeField(auto_now_add=True)
user = models.ForeignKey(GCUser, related_name='user_connection')
event = models.ForeignKey(Event, related_name='event_connection')
role = models.CharField(max_length=8, choices=constants.Roles.ROLE_CHOICES,)
class Event(Game):
creation_date = models.DateTimeField(auto_now_add=True)
public = models.BooleanField(default=False)
start_time = models.DateTimeField(null=True, blank=True)
end_time = models.DateTimeField(null=True, blank=True)
gm_is_player = models.BooleanField(default=False,
help_text='Check if GM will be playing the game',
verbose_name='GM is a player')
gm_is_designer = models.BooleanField(default=False, help_text='Check if GM designed the game')
user_notes = models.TextField(blank=True, default='', verbose_name='Note to Scheduler')
scheduler_notes = models.TextField(blank=True, default='')
experience = models.CharField(max_length=3, choices=constants.ExpLevels.EXPERIENCE_CHOICES,
default=constants.ExpLevels.NOVICE,)
status = models.CharField(max_length=4, db_index=True,
choices=constants.Status.STATUS_CHOICES,)
Here's my code:
class FilteredListSerializer(serializers.ListSerializer):
def to_representation(self, data):
data = data.filter(status=constants.Status.ASSIGNED).order_by('start_time')
return super(FilteredListSerializer, self).to_representation(data)
class UserEventSerializer(serializers.ModelSerializer):
class Meta:
list_serializer_class = FilteredListSerializer
model = models.Event
fields = ('id', 'event_name', 'conflict_type', 'start_time', 'end_time')
class UserConnectionSerializer(serializers.ModelSerializer):
event = UserEventSerializer()
class Meta:
model = models.Connection
fields = ('get_role_display', 'conflict_type', 'event')
class GCUserSerializer(serializers.ModelSerializer):
user_connection = UserConnectionSerializer(many=True)
class Meta:
model = models.GCUser
fields = ('pk', 'first_name', 'last_name', 'email',
'is_member', 'age', 'user_connection')
PyCharm tells me that "class FilteredListSerializer must implement all abstract methods" but it doesn't actually throw an error. I put a breakpoint at the first line of the list serializer, but it doesn't get tripped.
I'm using Python 3.4 with django 1.7.
Thanks in advance for your help.
Edited to add: Looking into the serializer code, I realized what may be the key difference: my call has many=True, whereas the one from the previous post didn't. I tried taking out the model=, but as expected that threw an error, so apparently the "working" code in the earlier post didn't actually run as written.
So I am not sure how to use the method you are using, but, if I understand your question correctly, I believe you could do something like this:
class UserEventSerializer(serializers.ModelSerializer):
class Meta:
model = models.Event
fields = ('id', 'event_name', 'conflict_type', 'start_time', 'end_time')
class UserConnectionSerializer(serializers.ModelSerializer):
event = serializers.SerializerMethodField()
class Meta:
model = models.Connection
fields = ('get_role_display', 'conflict_type', 'event')
def get_event(self, obj):
if obj.event.status == constants.Status.ASSIGNED:
serializer = UserEventSerializer(obj.event)
return serializer.data
else:
serializer = UserEventSerializer(None)
return serializer.data
N.B. This assumes that you are trying to exclude Events from being serialized if their status is not assigned.
I hope this helps. If I didn't understand the problem, let me know.
it's not a bug or error. ModelSerializer has got already implemented all needed methods (most inhereted from Serializer class), but ListSerializer inherits from BaseSerializer and got implemented e.g.: .create() or .to_representation(), but not .update(). I've got some similar problems in PyCharm, when subclassing a Serializer. After implementing create, update and to_representation methods this issue was gone