How to use DRF serializers to use multiple serializers and also flatten the data sent - django-rest-framework

Question

I am struggling to figure out the best way to write these serializers.
I have a model like this
class Foo(models.Model):
db = models.CharField(max_length=30)
name = models.CharField(max_length=30)
schema = models.CharField(max_length=50)
table_name = models.CharField(max_length=50)
ext_type = models.CharField(max_length=100)
sample_by = models.CharField()
sample_by_val = models.CharField()
Next I have my serializer with something like this
class SaveSerializer(serializers.ModelSerializer): #
"""
Cannot figure out the best way to do this.
This is just an example serializer I had in mind.
I want to understand a cleaner/best way to do this.
"""
sample = SampleSerializer()
exts = ExtSerializer()
class Meta:
model = Foo
Here is the problem - The data to this view is sent in this format
{
"sample": {"sample_by":"weight", "sample_by_val":[30,50,60],"name":"test"}
"exts": {"ext_type": "BY WEIGHT", "table":"EMPLOYEE"},
"db" : "foobar",
"schema" : "abcd"
}
class ExtSerializer(serializers.Serializer):
table = serializers.CharField()
ext_type = serializers.CharField()
class SampleSerializer(serializers.Serializer):
sample_by = serializers.CharField()
# Similar ones for sample_by_val and name
I am struggling to write SaveSerializer. It needs to first check the data that is being sent in a particular format and pass it through some serializers. Then it needs to flatten out that data format to store it in the model itself.
Can someone help me understand the best way to do this? It will be very helpful! thanks

Answer 1

You can override the to_representation() and to_internal_value(), I think it's best way.
Here is an example
Sorry, I'll eat my word, just override create method like this:
#override create method of serializer, you can easily handle object creation.
def create(self, validated_data):
#first, pop sample and exts from validated data.
sample = validated_data.pop('sample')
exts = validated_data.pop('exts')
#then, create object
foo = Foo.objects.create(**validated_data, **sample, **exts) #flat validated_data, sample, and exts to create Foo.
return foo
#maybe you also want to handle representation, since the model of Foo doesn't has ext and sample fields
def to_representation(self, instance):
sample = SampleSerializer(instance).data #SampleSerializer will deserialize sample_by field of Foo instance.
exts = ExtSerializer(instance).data
instance.sample = sample
instance.exts = exts
return super(SaveSerializer, self).to_representation(instance)