Combine two model instances into one serialized object django rest framework - django

Question

How can i merge equal fields and append different values to the fields in the returned response into one, independent of the amount of objects? When accessing the enpoint, i currently get the following response:
[
{
"colors": [
"Red",
"Orange",
],
"styles": [
"Rock"
],
"application": [
"Wall"
],
"material": [
"Mosaic"
]
},
{
"colors": [
"Yellow",
],
"styles": [
"Mosaic"
],
"application": [
"Wall"
],
"material": [
"Ceramic"
]
}
]
While want to achieve something like the snippet bellow, where unique values are appended and equal fields are merged:
[
{
"colors": [
"Red",
"Orange",
"Yellow"
],
"styles": [
"Rock"
"Mosaic"
],
"application": [
"Wall"
],
"material": [
"Mosaic"
"Ceramic"
]
},
]
My serializer is structured like this:
class ProductFiltersByCategorySerializer(serializers.ModelSerializer):
"""
A serializer to display available filters for a product lust
"""
colors = serializers.StringRelatedField(read_only=True, many=True)
styles = serializers.StringRelatedField(read_only=True, many=True)
application = serializers.StringRelatedField(read_only=True, many=True)
material = serializers.StringRelatedField(read_only=True, many=True)
class Meta:
model = Product
fields = (
'colors',
'styles',
'application',
'material'
)
My viewset is structured like this:
class ProductFiltersByCategory(generics.ListAPIView):
"""
This viewset takes the category parameter from the url and returns related product filters
"""
serializer_class = ProductFiltersByCategorySerializer
def get_queryset(self):
category = self.kwargs['category']
return Product.objects.filter(category__parent__name__iexact=category).distinct()
The fields colors, styles, application and material are ManytoMany relations to their own models from the Product model.5
Update 1: (Models)
class ProductSize(models.Model):
...
class ProductColor(models.Model):
...
class ProductStyle(models.Model):
...
class ProductApplication(models.Model):
...
class ProductMaterial(models.Model):
...
class Product(models.Model):
...
colors = models.ManyToManyField(
ProductColor,
related_name='product_color'
)
styles = models.ManyToManyField(
ProductStyle,
related_name='product_style'
)
application = models.ManyToManyField(
ProductApplication,
related_name='product_application'
)
material = models.ManyToManyField(
ProductMaterial,
related_name='product_material'
)
absorption = models.FloatField(
null=True,
blank=True
)
...

Answer 1

This is because your query returns two objects and each object has some related field. Serializers serialize each object separately so you should merge fields in your view that is responsible for the logic of the application, for this if your database is postgres you can use some code like this:
from django.contrib.postgres.aggregates import ArrayAgg
Product.objects.filter(category__parent__name__iexact=category).distinct().aggregate(colors_field=ArrayAgg('colors__name'))
or you can write separate query for each field.