Django Rest Framework serialize additional fields from intermediate model - django

Question

I am developing a small application that lists the customers of a store. I'm trying to retrieve the additional fields of the intermediate model because a contact can belong to several stores but depending on the store it is premium or not and if he is happy or not.
Here's the JSON response I'd like to get for a Store like /contacts/?store=my_store
[
{
"id": "UX",
"first_name": "UX",
"last_name": "UX",
"email": null,
"mobile": null,
"happy": True,
"premium": True
},
{
"id": "AX",
"first_name": "AX",
"last_name": "AX",
"email": null,
"mobile": null,
"happy": False,
"premium": True
}
]
here are my models:
class Store(BaseModel):
id = models.CharField(primary_key=True, max_length=200)
name = models.CharField(max_length=100)
class Contact(BaseModel):
id = models.CharField(primary_key=True, max_length=200)
first_name = models.CharField(max_length=100, null=True, blank=True)
last_name = models.CharField(max_length=100, null=True, blank=True)
email = models.CharField(max_length=100, null=True, blank=True)
mobile = models.CharField(max_length=100, null=True, blank=True)
stores = models.ManyToManyField(
Store, through="MemberShip", through_fields=("contact", "store")
)
class MemberShip(BaseModel):
contact = models.ForeignKey(
Contact, on_delete=models.CASCADE, related_name="contact_to_store"
)
store = models.ForeignKey(
Store, on_delete=models.CASCADE, related_name="store_to_contact"
)
happy = models.BooleanField(default=True)
premium = models.BooleanField(default=False)
and my serializers:
class MemberShipSerializer(serializers.ModelSerializer):
class Meta:
model = MemberShip
fields = ("contact", "store", "happy", "premium")
class StoreSerializer(serializers.ModelSerializer):
class Meta:
model = Store
fields = ("id", "name")
class ContactSerializer(serializers.ModelSerializer):
infos = MemberShipSerializer(
source="contact_to_store" many=True, read_only=True
)
class Meta:
model = Contact
fields = (
"id", "first_name", "last_name", "email", "mobile", "infos"
)
As you can see, I first tried to gather all the information of the intermediate model in a field before displaying happy and premium but, strangely enough, the infos field is returned with an empty array value.
Python v 3.7
Django v 2.1
DRF v 3.9

Answer 1

You must provide data to MemberShipSerializer . You can use SerializerMethodField. Like that:
class ContactSerializer(serializers.ModelSerializer):
infos = serializers.SerializerMethodField(read_only=True)
class Meta:
model = Contact
fields = (
"id", "first_name", "last_name", "email", "mobile", "infos"
)
def get_infos(self,obj:Contact):
return MemberShipSerializer(obj.contact_to_store.all(),many=True).data

Answer 2

I tried kamilyrb's solution here's what I changed:
class MemberShipSerializer(serializers.ModelSerializer):
class Meta:
model = MemberShip
fields = ("contact", "store", "happy", "premium")
class StoreSerializer(serializers.ModelSerializer):
class Meta:
model = Store
fields = ("id", "name")
class ContactSerializer(serializers.ModelSerializer):
happy = serializers.SerializerMethodField(read_only=True)
premium = serializers.SerializerMethodField(read_only=True)
class Meta:
model = Contact
fields = (
"id", "first_name", "last_name", "email", "mobile", "happy", "premium"
)
def get_premium(self, obj):
return MemberShipSerializer(obj.contact_to_store.all(), many=True).data
def get_happy(self, obj):
return MemberShipSerializer(obj.contact_to_store.all(), many=True).data
This is what i have now:
[
{
"id": "UX",
"first_name": "UX",
"last_name": "UX",
"email": "0",
"mobile": null,
"happy": [
{
"store": "my-store",
"contact": "UX",
"happy": true,
"premium": false,
},
{
"store": "my-store2",
"contact": "UX",
"happy": false,
"premium": false,
}
],
"premium": [
{
"store": "my-store",
"contact": "UX",
"optin_sms": true,
"happy": false,
"premium": false
}
]
}
]
how can i get that ?
[
{
"id": "UX",
"first_name": "UX",
"last_name": "UX",
"email": null,
"mobile": null,
"happy": True,
"premium": True
},
{
"id": "AX",
"first_name": "AX",
"last_name": "AX",
"email": null,
"mobile": null,
"happy": False,
"premium": True
}
]
I also noticed that all the stores to which a contact is affiliated are shown but as I said before the url is called as follows contact/?store=my-store