depth = 1 doesn't work properly and it's saves Null in ManyToManyField and ForeignKey fields in Django Rest Framework - json

Question

after adding depth = 1 doesn't work properly
=> models.py file
class State(models.Model):
state_name = models.CharField(max_length = 30, unique=True)
def __unicode__(self):
return str(self.state_name)
class City(models.Model):
state = models.ForeignKey(State, related_name='state_city')
city_name = models.CharField(max_length = 30)
def __unicode__(self):
return str(self.city_name)
class Meta:
ordering = ('city_name',)
unique_together = ('state', 'city_name',)
class Snippet(models.Model):
created = models.DateTimeField(auto_now_add=True)
title = models.CharField(max_length=100, blank=True, default='')
code = models.TextField()
linenos = models.BooleanField(default=False)
owner = models.ForeignKey('auth.User', related_name='snippets')
state = models.ForeignKey(State,blank=True,null=True)
city = models.ManyToManyField(City)
=> serializers.py file
class StateSerializer(serializers.ModelSerializer):
class Meta:
model = State
class CitySerializer(serializers.ModelSerializer):
state_name = serializers.CharField(source='state.state_name', read_only=True)
class Meta:
model = City
class SnippetSerializer(serializers.ModelSerializer):
owner = serializers.ReadOnlyField(source='owner.username', read_only=True)
class Meta:
model = Snippet
fields = ('id', 'title', 'code', 'linenos', 'owner', 'state', 'city')
depth = 1
I have added ForeignKey and ManyToManyField fields in state and city respectively. It doesn't save values in SnippetSerializer while added depth = 1 in Meta Class (it saves Null value in state and city fields). When I add depth = 1 JSON showing related fields as it should be but it doesn't work properly while add new Snippet. Without depth = 1 it works fine.
I have complex database where tables has many ManyToMany and ForeignKey related fields. Please give me suggestion so I can get related data in JSON.
I have djangorestframework-3.1.2 version. I have used latest version too but same problem. please give me solution and thanks in advance.

Answer 1

I faced the same problem and managed to solve it. Since the problem is with the depth, I just change the depth value in the init method.
class SnippetSerializer(serializers.ModelSerializer):
owner = serializers.ReadOnlyField(source='owner.username', read_only=True)
class Meta:
model = Snippet
fields = ('id', 'title', 'code', 'linenos', 'owner', 'state', 'city')
depth = 1
def __init__(self, *args, **kwargs):
super(SnippetSerializer, self).__init__(*args, **kwargs)
request = self.context.get('request')
if request and request.method=='POST':
self.Meta.depth = 0
else:
self.Meta.depth = 1
In the code above, I changed the depth dynamically according to what type of request that I made.
But, this is the workaround that I found myself, I'm not sure if this is the best practice but it solve the problem with just little modification.

Answer 2

depth is only for representation (http://www.django-rest-framework.org/api-guide/serializers/#specifying-nested-serialization). If you want to create/update the related fields too you have to overwrite the create/update methods in the serializer (http://www.django-rest-framework.org/api-guide/relations/#writable-nested-serializers).
Greetings.