How to change default behavior of serializers - django

Question

I am doing some stuff with the django restframework. Very basic now, but I like to have my data coming back to me bit differently.
This is how I get the response now:
[
{
"line": "line1",
"user_text": "Some text",
"topic": "value/xrp"
},
{
"line": "line2",
"user_text": "Some text 2",
"topic": "beer/heineken/sale"
}
]
This is what I like to get:
{
"line1": {
"user_text": "Some text",
"topic": "value/xrp"
},
"line2": {
"user_text": "Some text 2",
"topic": "beer/heineken/sale"
}
}
This is my serializer:
class LineSerializer(serializers.Serializer):
line = serializers.CharField(max_length=16)
user_text = serializers.CharField(max_length=16)
topic = serializers.CharField()
This is the view
class DisplayDetailAPIView(ListAPIView):
serializer_class = LineSerializer
def get_queryset(self):
return Line.objects.filter(display__serial_number=self.kwargs['serial_number'])
And the model (as reference)
class Line(models.Model):
display = models.ForeignKey(Display, on_delete=models.CASCADE, related_name='lines')
line = models.CharField(max_length=16)
user_text = models.CharField(max_length=16, null=True, blank=True)
topic = models.ForeignKey(Topic, on_delete=models.CASCADE, blank=True, null=True)
def __str__(self):
return self.line
I looked in the rest framework documentation and a bit here on stackoverflow but I could not find an answer yet.
If someone has hints for me that would be very much appreciated :)

Answer 1

You can override to_representation in your serializer class:
class LineSerializer(serializers.ModelSerializer):
class Meta:
model = Line
fields = ('user_text', 'topic')
def to_representation(self, instance):
data = super().to_representation(instance)
response_data = {}
response_data[instance.line] = data
return response_data
You just create a temporary data dictionary and assign the current instance line attribute to be the key of your JSON response - what you actually want to have in the end:
[
{
"line1": {
"user_text": "lorem ipsum",
"topic": ...
}
},
{
"line2": {
"user_text": "dolor sin amet",
"topic": ...
}
}
]
Note 1: You may want to use a ModelSerializer instead of Serializer in this particular case, I think it is more straightforward to use and you can access instance.line directly, without specifying it actually to be serialized.
Note 2: Here your topic field will be serialized as an id since it is a ForeignKey relation on a database level. If you want to serialize topic as a CharField from one of the actual topic's fields, have a look here.