Reformat Django REST Framework Serializer to get Output - django

Question

I am trying to get data in a particular format but i'm not able to get the desired output.
My Model:
class Category(models.Model):
name = models.CharField(max_length=40)
class Expense(models.Model):
category = models.ForeignKey(Category, on_delete=models.CASCADE, related_name="category_name")
description = models.CharField(max_length=200)
total_amount = models.IntegerField()
class Expense_Details(models.Model):
expense = models.ForeignKey(Expense, on_delete=models.CASCADE, related_name="payment")
user = models.IntegerField()
amount = models.FloatField()
type = models.CharField(max_length=100) ---->type is owe or lend
When I request /api/expenses/:
Expected Output
{
“total_expenses”: 10,
“Expenses”:
[{
“id”: 1,
“category”: 1,
“created_by”: 1, ------> user logged id
“description”: “lunch”,
“total_amount”: “105”,
“owe”: [{
“user_id”: 1,
“amount”: 10
},
{
“user_id”: 2,
“amount”: 95
}],
“lend”: [{
“user_id”: 3,
“amount”: 10
},
{
“user_id”: 4,
“amount”: 95
}],
}, ...
]
}
My output:
{
"results": [
{
"id": 1,
"category": 1,
"description": "lunch at the burj al arab",
"total_amount": 105,
"payment": [
{
"user": 1,
"amount": -10
},
{
"user": 2,
"amount": -95
},
{
"user": 3,
"amount": 10
},
{
"user": 4,
"amount": 95
}
]
}
]
}
My Serializer:
class ExpenseDetailsSerializer(serializers.ModelSerializer):
class Meta:
model = Expense_Details
fields = ['user', 'amount']
class ExpenseSerializer(serializers.ModelSerializer):
payment = serializers.SerializerMethodField()
def get_payment(self, obj):
return ExpenseDetailsSerializer(obj.payment.all(), many=True).data
class Meta:
model = Expense
fields = ['id', 'category', 'description', 'total_amount', 'payment',]
What Query should I use to get Output in the above format? How will my serializer look like? How can I separate own and lend? Also I have stored own and lend with + and - sign to differentiate between them.

Answer 1

Use a ListField for the same.
Documentation: https://www.django-rest-framework.org/api-guide/fields/#listfield
Also refer How to serialize an 'object list' in Django REST Framework
Here you can try something like:
class ExpenseSerializer(serializers.Serializer):
payment = serializers.ListField(child=ExpenseDetailsSerializer())
def get_payment(self, obj):
return ExpenseDetailsSerializer(obj.payment.all(), many=True).data
class Meta:
model = Expense
fields = ['id', 'category', 'description', 'total_amount', 'payment',]