Serializers in django rest framework with dynamic fields - django

Question

I am trying to build a small api with django rest framework but I don't want to map directly the tables with calls (as in the examples).
I have the following database schema:
In models.py:
class ProductType(models.Model):
name = models.CharField(max_length=255, blank=False, null=False, unique=True)
class Product(models.Model):
#staticmethod
def get_accepted_fields(self):
return {'color': 'pink', 'size': 34, 'speed': 0, 'another_prop': ''}
name = models.CharField(max_length=255, blank=False, null=False, unique=True)
class ProductConfig(models.Model):
product_type = models.ForeignKey(ProductType)
product = models.ForeignKey(Product)
# a json field with all kind of fields: eg: {"price": 123, "color": "red"}
value = models.TextField(blank=True)
As you can see, every product can have multiple configurations and the value field is a json with different parameters. The json will be one level only. The configuration will have a flag if is active or not (so, the 1 product will have only 1 active configuration)
So, the data will look for example like this:
store_producttype
=================
1 type1
2 type2
store_product
=============
id name
1 car
store_productconfig
===================
id product_type_id product_id value active
1 2 1 { "color": "red", "size": 34, "speed": 342} 0
2 1 1 { "color": "blue", "size": 36, "speed": 123, "another_prop": "xxx"} 1
What I want to know is how can I get /product/1/ like this:
{
"id": 1,
"name": "car",
"type": "type1",
"color": "blue",
"size": 36,
"speed": 123,
"another_prop": "xxx",
}
and to create a new product posting a json similar with the one above.
The json fields are defined but some of them can miss (eg: "another_prop" in the productconfig.id=1
On update, anyway, it will create a new row in productconfig and it will put inactive=0 on the previous one.
So, every product can have different configuration and I want to go back to a specific configuration back in time in some specific cases). I am not really bound to this data model, so if you have suggentions for improvement I am open to them, but I don't want to have that properties as columns in the table.
The question is, what will be the best way to write the serializers for this model? There is any good example somewhere for a such use case?
Thank you.

Answer 1

Let's take this step by step:
In order to get a JSON like the one you posted, you must first transform your string (productConfig value field) to a dictionary. This can be done by using ast.literal_eval ( see more here).
Then, in your product serializer, you must specify the source for each field, like this:
class ProductSerializer(serializers.ModelSerializer):
color = serializer.Field(source='value_dict.color')
size = serializer.Field(source='value_dict.size')
type = serializer.Field(source='type.name')
class Meta:
model = Product
fields = (
'id',
'color',
'size',
'type',
)
This should work just fine for creating the representation that you want. However, this will not create automatically the product config, because DRF doesn't yet allow nested object creation.
This leads us to the next step:
For creating a product with a configuration from JSON, you must override the post method in your view, and create it yourself. This part shouldn't be so hard, but if you need an example, just ask.
This is more of a suggestion: if the json fields are already defined, wouldn't it be easier to define them as separate fields in your productConfig model?