Django Rest Framework - Group data by dynamic Key - django

Question

I'm trying to format data when querying my API. I can retrieve my data like that :
"results": [
{
"Cat1": [
{
"job": String,
"position": Integer
}
]
},
{
"Cat1": [
{
"job": String,
"position": Integer
}
]
},
{
"Cat2": [
{
"job": String,
"position": Integer
}
]
}
]
But I want something like that:
"results": [
{
"Cat1": [
{
"job": String,
"position": Integer
},
{
"job": String,
"position": Integer
}
]
},
{
"Cat2": [
{
"job": String,
"position": Integer
}
]
}
]
I use a serializer like this:
class CustomSerializer(serializers.ModelSerializer):
category = CatSerializer()
job = JobSerializer()
class Meta:
model = MyModel
fields = '__all__'
def to_representation(self, value):
return {
value.category.name: [{"job": value.job.name,
"position": value.position, }]
cat1 and cat2 are dynamics, they are from another table. I don't understand how to create my arrays properly using those serializers. The category is a #Property field in my model who's a foreign key of job.
My models:
class MyModel(models.Model):
CHOICES = [(i, i) for i in range(4)]
partner = models.ForeignKey(Partner, on_delete=models.CASCADE)
job = models.ForeignKey(
Job, on_delete=models.CASCADE)
position = models.IntegerField(choices=CHOICES)
#property
def category(self):
return self.job.category.domain
def __str__(self):
return '%s | %s | %s | position: %s' % (self.partner.name, self.domain.name, self.job.name, self.position)
class Job(models.Model):
category = models.ForeignKey(Category, on_delete=models.CASCADE)
code = models.CharField(
max_length=255, unique=True)
name = models.CharField(
max_length=255)
class Category(models.Model):
domain = models.ForeignKey(Domain, on_delete=models.CASCADE)
code = models.CharField(
max_length=5)
name = models.CharField(max_length=255)
hourly_rate = models.FloatField(
null=True, blank=True)
How should I deal with serializers to format my data properly ?
EDIT:
I ended with something like that, except for the ListSerializer.
I used 2 ModelSerilizers
class MyModelCustomSerializer(serializers.ModelSerializer):
position = serializers.IntegerField(read_only=True)
job = serializers.CharField(source='job.name', read_only=True)
class Meta:
model = MyModel
fields = ['job', 'position']
def to_representation(self, value):
return {"position": value.position,
"job": {"name": value.job.name, "slug": value.job.slug,
"title": value.job.seo_title}
}
And
class CategoryCustomSerializer(serializers.ModelSerializer):
models = MyModelustomerSerializer(many=True)
class Meta:
model = Category
fields = ['category', 'MyModel']
def to_representation(self, value):
filters = {'job__category__domain__name': value.name}
myModels = MyModel.objects.filter(**filters)
serializer = MyModelCustomSerializer(instance=myModels, many=True,)
return {value.name: serializer.data}
But if I try to use a jobSerializer who already exist instead of
"job": {"name": value.job.name, "slug": value.job.slug,
"title": value.job.seo_title}
},
I got this error: Object of type 'Job' is not JSON serializable, but it's working anyway because i don't need all fields

Answer 1

I would go the direction of implementing a custom ListSerializer for the ModelSerializer and overriding its to_representation method.
from rest_framework import serializers
from collections import OrderedDict
class CustomListSerializer(serializers.ListSerializer):
def to_representation(self, data):
iterable = data.all() if isinstance(data, models.Manager) else data
list_rep = OrderedDict()
for item in iterable:
child_rep = self.child.to_representation(item)
k, v = list(child_rep.items()).pop()
list_rep.setdefault(k, []).append(v)
return [
{k: v}
for k, v in list_rep.items()
]
Then set the model Meta to use it
class CustomSerializer(serializers.ModelSerializer):
category = CatSerializer()
job = JobSerializer()
class Meta:
model = MyModel
fields = '__all__'
list_serializer_class = CustomListSerializer
def to_representation(self, value):
return {
value.category.name: [{"job": value.job.name,
"position": value.position, }]