DRF How to change the field key names in JSON response - django

Question

I want to display all objects of a particular model, and it's related objects ( object-wise ).
Is there a way to change/customize the JSON output? (In terms of the key names, values, or the nesting?)
views.py
#api_view(['GET'])
def api(request):
q = Question.objects.all()
s = QuestionSerializer(q, many=True)
print(ChoiceSerializer())
return Response(s.data)
serializers.py
class QuestionSerializer(serializers.ModelSerializer):
choices = serializers.PrimaryKeyRelatedField(many=True, read_only=True)
class Meta:
model = Question
fields = '__all__'
models.py
class Question(models.Model):
question_text = models.CharField(max_length=200)
pub_date = models.DateTimeField(auto_now_add=True, editable=False, name='pub_date')
def __str__(self):
return self.question_text
def was_published_recently(self):
now = timezone.now()
return now - datetime.timedelta(days=1) <= self.pub_date <= now
class Choice(models.Model):
question = models.ForeignKey(Question, on_delete=models.CASCADE, related_name='choices')
choice_text = models.CharField(max_length=200)
votes = models.IntegerField(default=0)
def __str__(self):
return self.choice_text
def related_question(self):
q = self.question.question_text
return q
Output
HTTP 200 OK
Allow: OPTIONS, GET
Content-Type: application/json
Vary: Accept
[
{
"id": 1,
"choices": [
1,
2,
3
],
"question_text": "Question 1",
"pub_date": "2020-12-19T23:07:25.071171+05:30"
},
{
"id": 2,
"choices": [
4,
5
],
"question_text": "Question 2",
"pub_date": "2020-12-21T13:58:37.595672+05:30"
}
]
In the output, choices shows the pk of the objects.
How can I change that to show, say, the choice_text or a custom string?
Also, can the way the objects are nested be customized?
EDIT: When I asked if there is a way to exercise more control, I meant control over the depth of JSON response.

Answer 1

You can use serializer's method field to replace choices key with any related model fields that you want. For instance
class QuestionSerializer(serializers.ModelSerializer):
choices = serializers.SerializerMethodField('get_choices')
class Meta:
model = Question
fields = '__all__'
def get_choices(self, obj):
return obj.choices.values('choice_text').distinct() # or values('id', 'choice_text') based on your requirements
Note that values are a better way than iterating through all objects as a performance point of view (like [choice.choice_text for choice in question.choices.all()], etc).
EDIT: SerializerMethodField is used when we want to run some custom logic to populate a particular field.
When using ModelSerializer, the source keyword can be used to access fields (related, non related both) or even rename fields in the case where the person interacting with the endpoint requires a different name.
Example for renaming(using models mentioned in the question)
class QuestionSerializer(serializers.ModelSerializer):
poll_question = serializers.CharField(source='question_text')
class Meta:
model = Question
fields = '__all__'
Example for getting a FK related field:
class ChoiceSerializer(serializers.ModelSerializer):
poll_question = serializers.CharField(source='question.question_text')
class Meta:
model = Choice
fields = '__all__'
This is a very good foundational read for understanding how and when to use serializers in DRF.

Answer 2

You can use serializers.SerializerMethodField(...) if you want more control over what you wish to return
class QuestionSerializer(serializers.ModelSerializer):
choices = serializers.SerializerMethodField()
def get_choices(self, question):
return [choice.choice_text for choice in question.choices.all()]
class Meta:
model = Question
fields = '__all__'

Answer 3

Instead of PrimaryKeyRelatedField, consider using SlugRelatedField. For example:
class QuestionSerializer(serializers.ModelSerializer):
choices = SlugRelatedField(many=True, read_only=True, slug_field='choice_text')
class Meta:
model = Question
fields = '__all__'
Also, you need to make choice_text field unique, ie add unique=True for this to work.
choice_text = models.CharField(max_length=200, unique=True)
FYI, you can remove __unicode__ method from your model definations. Explanation can be found in this Django documentation link.