How to create dynamic rest ModelSerializer? - python-3.x

Question

I'm currently working on a big code base and i need to send emails from any potential module, that conduct in Circular Dependencies issues in python
so i tried to use apps.get_model() from django.apps but when serializers are declared the models are not ready.
So i'm trying to create a factory function who build the class at runtime instead of launch time
from rest_framework.serializers import ModelSerializer
def make_serializer(model: str, fields: tuple, options = None, **nested_fields) -> ModelSerializer:
"""Generate a new serializer "On the fly", so the model does not have to be imported at launch time.
"""
model_object = apps.get_model(model)
input_fields = fields
if options is None:
options = {}
class Serializer(ModelSerializer):
class Meta:
model = model_object
fields = input_fields
def create(self, validated_data):
# we won't permit to create data from thoses serializers.
raise NotImplementedError
# configure nested serializers.
for nested_field in nested_fields.values():
for key, nested_serializer_class in nested_field.items():
serializer_instance = nested_serializer_class(**options.get(key, {}))
print(model, key, serializer_instance)
setattr(Serializer, key, serializer_instance)
return Serializer
my tests models looks like
class Band(Model):
name = Charfield(max_length=255)
class Influencer(Model):
entity = Charfield(max_length=255)
class Submission(Model):
influencer = ForeignKey(Influencer, ...)
class Campaign(Model):
band = ForeignKey('band.Band', ...)
submissions = ManyToMany(Submission)
and my testing function is:
def test():
serializer = make_serializer(
model='submission.Campaign',
fields=['pk', 'submissions', 'band'],
options={'submissions': {'many': True}},
nested_fields={
'submissions': make_serializer(
model='submission.Submission',
fields=('influencer',),
nested_fields={
'influencer': make_serializer('influencer.Influencer', ('entity',))
},
),
'band': make_serializer('band.Band', ('name',))
}
)
return serializer
instead of having my fields correly with test()(Campaign.objects.last()).data i only got "pks" and my serialiser looks like:
Serializer():
pk = IntegerField(label='ID', read_only=True)
submissions = PrimaryKeyRelatedField(many=True, queryset=Submission.objects.all())
band = PrimaryKeyRelatedField(allow_null=True, queryset=Band.objects.all(), required=False)
i except and output like:
{
"pk": 1,
"band": {
"name": "BobMarley",
},
"submissions": [
{
"influencer": {"entity": "The influencer's name"}
}
]
}
but i got a ReturnDict containing:
{
"pk": 1,
"band": 523,
"submissions": [6, 7, 8]
}
thanks for your time

Answer 1

well after many headcaches i've found out that i CAN'T setattr on a class after it's declaration, so i use a trick based on a dict
def make_serializer(model: str, fields: tuple, options = None, **nested_fields) -> ModelSerializer:
"""Generate a new serializer "On the fly", so the model does not have to be imported at launch time.
"""
name = f'Serializer_{model}'
model_object = apps.get_model(model)
input_fields = fields
if options is None:
options = {}
def create(self, validated_data):
# we won't permit to create data from thoses serializers.
raise NotImplementedError
class Meta:
model = model_object
fields = input_fields
attrs = {"Meta": Meta}
# configure nested serializers.
for key, nested_serializer_class in nested_fields.items():
attrs[key] = nested_serializer_class(**options.get(key, {}))
attrs['create'] = create
return type(ModelDictSerializer)(name, (ModelDictSerializer,), attrs)
the syntax is something like:
campaign_serializer = make_serializer(
model='submission.Campaign',
fields=['pk', 'submissions', 'band'],
options={'submissions': {'many': True}},
submissions=make_serializer(
model='submission.Submission',
fields=('influencer',),
influencer=make_serializer('influencer.Influencer', ('entity',))
),
band=make_serializer('band.Band', ('name',))
)
and it's working like a charm:
Serializer_submission.Campaign(<Campaign: Campaign object (9665)>):
pk = IntegerField(label='ID', read_only=True)
submissions = Serializer_submission.Submission(many=True):
influencer = Serializer_influencer.Influencer():
entity = CharField(allow_blank=True, max_length=255, required=False)
band = Serializer_band.Band():
name = CharField(max_length=255)
i hope this will help someone else