I have a model with a self referential field called parent.
Model:
class Zone(BaseModel):
name = models.CharField(max_length=200)
parent = models.ForeignKey('self', models.CASCADE, blank=True, null=True, related_name='children')
def __unicode__(self):
return self.name
Serializer:
class ZoneSerializer(ModelSerializer):
parent = PrimaryKeyRelatedField(many=False, queryset=Zone.objects.all())
parent_disp = StringRelatedField(many=False, source="parent")
class Meta:
model = Zone
fields = ('id', 'name', 'parent', 'parent_disp')
Now I want to serialize the parent of the zone and its parent and its parent till parent is none.
I found recursive serialization methods for children but not for parent.
How can I do this?
Ok, I got it working like that.
class ZoneSerializer(ModelSerializer):
parent = SerializerMethodField()
class Meta:
model = Zone
fields = ('id', 'name', 'project', 'parent',)
def get_parent(self, obj):
if obj.parent is not None:
return ZoneSerializer(obj.parent).data
else:
return None
Try use SerializerMethodField here:
def get_parent(self, obj):
# query what your want here.
I'm not sure D-R-F has build-in methods for this, but you can use query to get what you want in this method.
You also can do:
class ZoneSerializer(ModelSerializer):
class Meta:
model = Zone
fields = ('id', 'name', 'project', 'parent',)
def to_representation(self, instance):
self.fields['parent'] = ZoneSerializer(read_only=True)
return super(ZoneSerializer, self).to_representation(instance)
Just wanted to add an additional solution that worked better for me.
The answer above using the SerializerMethodField and then instantiating a new serializer class works nicely, but if you are trying to serialize a larger nested dataset instantiating a new serializer for each of your nested objects might become quite slow.
Trying to use a single instance of the serializer for all the nested objects made it a lot faster.
class ZoneSerializer(ModelSerializer):
...
def get_parent(self, obj):
if obj.parent is not None:
return self.to_representation(obj)
else:
return None
One more step could be to also convert your return of the serializer method field to a ReturnDict instance, which is what a serializer normally does when you call serializer.data property.
from rest_framework.utils.serializer_helpers import ReturnDict
class ZoneSerializer(ModelSerializer):
...
def get_parent(self, obj):
if obj.parent is not None:
return ReturnDict(self.to_representation(obj), serializer=self)
else:
return None
There are some potential disadvantages of this approach of course, like loosing validation that happens when instantiating a serializer, harder to modify for nested objects, etc.
If you are confident in your serializer setup and data being passed to the serializer this can be a nice optimization.
Related
Here is my view:
class SectorListAPI(generics.ListAPIView):
queryset = SectorModel.objects.all()
serializer_class = SectorSerializer
Here is my serializers:
class OrganizationSerializer(serializers.ModelSerializer):
class Meta:
model = GroupProfile
fields = ('title','slug',)
class DepartmentSerializer(serializers.ModelSerializer):
organizations = OrganizationSerializer(many=True, read_only=True)
class Meta:
model = DepartmentModel
fields = ('title', 'organizations',)
class SectorSerializer(serializers.ModelSerializer):
# title = serializers.CharField()
departments = DepartmentSerializer(many=True, read_only=True)
class Meta:
model = SectorModel
fields = ('title','departments',)
Look, here 'SectorSerializer' is parent 'DepartmentSerializer' is children and 'OrganizationSerializer' is grand children serializer. Now in my view I can easily filter my queryset for 'SectorModel'. But how can i filter on 'GroupProfile' model.
You might want to filter the queryset to ensure that only results relevant to the currently authenticated user making the request are returned.
You can do so by filtering based on the value of request.user.
For example:
from myapp.models import Purchase
from myapp.serializers import PurchaseSerializer
from rest_framework import generics
class PurchaseList(generics.ListAPIView):
serializer_class = PurchaseSerializer
def get_queryset(self):
"""
This view should return a list of all the purchases
for the currently authenticated user.
"""
user = self.request.user
return Purchase.objects.filter(purchaser=user)
EDIT
You can subclass the ListSerializer and overwrite the to_representation method.
By default the to_representation method calls data.all() on the nested queryset. So you effectively need to make data = data.filter(**your_filters) before the method is called. Then you need to add your subclassed ListSerializer as the list_serializer_class on the meta of the nested serializer.
1- subclass ListSerializer, overwriting to_representation and then calling super
2- Add subclassed ListSerializer as the meta list_serializer_class on the nested Serializer.
Code relevant to yours:
class FilteredListSerializer(serializers.ListSerializer):
def to_representation(self, data):
data = data.filter(user=self.request.user, edition__hide=False)
return super(FilteredListSerializer, self).to_representation(data)
class OrganizationSerializer(serializers.ModelSerializer):
class Meta:
list_serializer_class = FilteredListSerializer
model = GroupProfile
fields = ('title','slug',)
class DepartmentSerializer(serializers.ModelSerializer):
organizations = OrganizationSerializer(many=True, read_only=True)
class Meta:
model = DepartmentModel
fields = ('title', 'organizations',)
class SectorSerializer(serializers.ModelSerializer):
# title = serializers.CharField()
departments = DepartmentSerializer(many=True, read_only=True)
class Meta:
model = SectorModel
fields = ('title','departments',)
Thanks to #ans2human for the inspiration behind this answer.
Here's a new approach that is working great for me. I have several Models with is_active = BooleanField(...) that I need to filter out in nested relationships.
NOTE: this solution does not filter out results on non-list fields. for that, you should look to the primary queryset on your View
The core of the work is done by overloading the to_representation() function on a custom ListSerializer, and the many_init on an accompanying custom ModelSerializer:
class FilteredListSerializer(serializers.ListSerializer):
filter_params:dict
def __init__(self, *args, filter_params:dict={"is_active":True}, **kwargs):
super().__init__(*args, **kwargs)
self.filter_params = filter_params
def set_filter(self, **kwargs):
self.filter_params = kwargs
def to_representation(self, data):
data = data.filter(**self.filter_params)
return super().to_representation(data)
class FilteredModelSerializer(serializers.ModelSerializer):
LIST_SERIALIZER_KWARGS = serializers.LIST_SERIALIZER_KWARGS + ("filter_params",)
LIST_ONLY_KWARGS = ('allow_empty', 'filter_params')
#classmethod
def many_init(cls, *args, **kwargs):
list_kwargs = dict()
for arg in cls.LIST_ONLY_KWARGS:
value = kwargs.pop(arg, None)
if value is not None:
list_kwargs[arg] = value
child_serializer = cls(*args, **kwargs, **({"read_only":True} if "read_only" not in kwargs else dict()))
list_kwargs['child'] = child_serializer
list_kwargs.update({
key: value for key, value in kwargs.items()
if key in cls.LIST_SERIALIZER_KWARGS
})
meta = getattr(cls, 'Meta', None)
list_serializer_class = getattr(meta, 'list_serializer_class', FilteredListSerializer)
return list_serializer_class(*args, **list_kwargs)
Then, your custom ModelSerializer for whatever view would instead just extend FilteredModelSerializer instead.
class ChildSerializer(FilteredModelSerializer):
is_active = BooleanField() # not strictly necessary, just for visibilty
... # the rest of your serializer
class ParentSerializer(serializers.ModelSerializer):
children = ChildSerializer(many=True)
...# the rest of your parent serializer
Now, the children field on the ParentSerializer will filter for is_active = True.
If you have a custom query that you wanted to apply, you can do so by providing a dict of filter params in the standard queryset format:
class ParentSerializer(serializers.ModelSerializer):
children = ChildSerializer(many=True, filter_params={"my_field":my_value, "my_datetime__gte": timezone.now()})
...# the rest of your parent serializer
Alternatively, one could also utilize the set_filter(...) method on the FilteredListSerializer after instantiating the field, like so. This will yield a more familiar format to the original QuerySet.filter(...) style:
class ParentSerializer(serializers.ModelSerializer):
children = ChildSerializer(many=True)
children.set_filter(my_field=my_value, my_datetime__gte=timezone.now())
...# the rest of your parent serializer
I need to add a static field to my serializer. It should always return the same value, regardless of the passed object. Currently I implemented it like so:
class QuestionSerializer(serializers.ModelSerializer):
type = serializers.SerializerMethodField()
#staticmethod
def get_type(obj):
return 'question'
class Meta:
model = Question
fields = ('type',)
But is there a simpler way to do it, without the SerializerMethodField?
using a ReadOnlyField worked for me:
class QuestionSerializer(serializers.ModelSerializer):
type = serializers.ReadOnlyField(default='question')
class Meta:
model = Question
fields = ('type',)
https://www.django-rest-framework.org/api-guide/fields/#readonlyfield
The only alternative would be to override to_representation and add the value there:
def to_representation(self, obj):
data = super().to_representation(obj)
data['type'] = 'question'
return data
Not a much better option though.
You can use serializers.HiddenField
class QuestionSerializer(serializers.ModelSerializer):
type = serializers.HiddenField(default='question')
class Meta:
model = Question
fields = ('type',)
http://www.django-rest-framework.org/api-guide/fields/#hiddenfield
If you don't care about adding a line to your model, it would be easier to add static field to your model.
class Question(models.Model):
type = 'question'
class QuestionSerializer(serializers.ModelSerializer):
class Meta:
model = Question
fields = ('type',)
I have this code
# Models
class NestedSample(models.Model):
something = models.CharField(max_length=255)
class Sample(models.Model):
thing = models.BooleanField()
nested = models.ForeignKey(NestedSample)
# Serializers
class NestedSampleSerializer(serializers.HyperlinkedModelSerializer):
class Meta:
model = api_models.NestedSample
class SampleSerializer(serializers.HyperlinkedModelSerializer):
nested = NestedSampleSerializer() # HERE filter delete=false
nested2 = NestedSample2Serializer() # HERE filter deletefalse
class Meta:
model = api_models.Sample
In my view I am overrding the queryset for delete=False but it is not applying to nested serializers.
delete=False in queryset will only filter Sample. To filter queryset in nested serializer you can use serializers.ListSerializer like:
class FilterDeleteListSerializer(serializers.ListSerializer):
def to_representation(self, data):
data = data.filter(delete=False)
return super(FilterDeleteListSerializer, self).to_representation(data)
class NestedSampleSerializer(serializers.HyperlinkedModelSerializer):
class Meta:
model = api_models.NestedSample
list_serializer_class = FilterDeleteListSerializer
class NestedSample2Serializer(serializers.HyperlinkedModelSerializer):
class Meta:
model = api_models.NestedSample2
list_serializer_class = FilterDeleteListSerializer
class SampleSerializer(serializers.HyperlinkedModelSerializer):
nested = NestedSampleSerializer() # HERE filter delete=false
nested2 = NestedSample2Serializer() # HERE filter deletefalse
class Meta:
model = api_models.Sample
Learn more here
I didn't exactly understand your question, but from what I figured you've got a boolean field in your Model which is set to True if you delete the object instead of actually deleting it from the database (SQL DELETE).
Now coming to your question, if you just want to filter the nested serializer then you could use the SerializerMethodField. You need to specify the method to call as an argument or add a method with the name 'get_' followed by the field name. In this method you can filter the queryset serialize it and return the data of that queryset.
class UserSerializer(serializers.ModelSerializer):
delete_filtered_items = serializers.SerializerMethodField()
class Meta:
model = User
def get_delete_filtered_items(self, obj):
items = Item.objects.filter(user=obj,deleted=False)
serializer = ItemsSerializer(instance=items, many=True)
return serializer.data
The above solution should work for your requirements, but if what you've implemented is similar to a soft delete then it would seem cleaner and more moduler to create a custom model manager.
I have some models like these:
class TypeBase(models.Model):
name = models.CharField(max_length=20)
class Meta:
abstract=True
class PersonType(TypeBase):
pass
class CompanyType(TypeBase):
pass
Having this, I want to create just one serializer that holds all these field types (serialization, deserialization, update and save).
To be more specific, I want only one serializer (TypeBaseSerializer) that print the Dropdown on the UI, serialize the json response, deserialize it on post and save it for all my based types.
Something like this:
class TypeBaseSerializer(serializers.Serializer):
class Meta:
model = TypeBase
fields = ('id', 'name')
Is it possible?
I think the following approach is more cleaner. You can set "abstract" field to true for the base serializer and add your common logic for all child serializers.
class TypeBaseSerializer(serializers.ModelSerializer):
class Meta:
model = TypeBase
fields = ('id', 'name')
abstract = True
def func(...):
# ... some logic
And then create child serializers and use them for data manipulation.
class PersonTypeSerializer(TypeBaseSerializer):
class Meta:
model = PersonType
fields = ('id', 'name')
class CompanyTypeSerializer(TypeBaseSerializer):
class Meta:
model = CompanyType
fields = ('id', 'name')
Now you can use the both of these serializers normally for every model.
But if you really want to have one serializers for both the models, then create a container model and a serializer for him too. That is much cleaner :)
You can't use a ModelSerializer with an abstract base model.
From restframework.serializers:
if model_meta.is_abstract_model(self.Meta.model):
raise ValueError(
'Cannot use ModelSerializer with Abstract Models.'
)
I wrote a serializer_factory function for a similar problem:
from collections import OrderedDict
from restframework.serializers import ModelSerializer
def serializer_factory(mdl, fields=None, **kwargss):
""" Generalized serializer factory to increase DRYness of code.
:param mdl: The model class that should be instanciated
:param fields: the fields that should be exclusively present on the serializer
:param kwargss: optional additional field specifications
:return: An awesome serializer
"""
def _get_declared_fields(attrs):
fields = [(field_name, attrs.pop(field_name))
for field_name, obj in list(attrs.items())
if isinstance(obj, Field)]
fields.sort(key=lambda x: x[1]._creation_counter)
return OrderedDict(fields)
# Create an object that will look like a base serializer
class Base(object):
pass
Base._declared_fields = _get_declared_fields(kwargss)
class MySerializer(Base, ModelSerializer):
class Meta:
model = mdl
if fields:
setattr(Meta, "fields", fields)
return MySerializer
You can then use the factory to produce serializers as needed:
def typebase_serializer_factory(mdl):
myserializer = serializer_factory(
mdl,fields=["id","name"],
#owner=HiddenField(default=CurrentUserDefault()),#Optional additional configuration for subclasses
)
return myserializer
Now instanciate different subclass serializers:
persontypeserializer = typebase_serializer_factory(PersonType)
companytypeserializer = typebase_serializer_factory(CompanyType)
As already mentioned in Sebastian Wozny's answer, you can't use a ModelSerializer with an abstract base model.
Also, there is nothing such as an abstract Serializer, as some other answers have suggested. So setting abstract = True on the Meta class of a serializer will not work.
However you need not use use a ModelSerializer as your base/parent serializer. You can use a Serializer and then take advantage of Django's multiple inheritance. Here is how it works:
class TypeBaseSerializer(serializers.Serializer):
# Need to re-declare fields since this is not a ModelSerializer
name = serializers.CharField()
id = serializers.CharField()
class Meta:
fields = ['id', 'name']
def someFunction(self):
#... will be available on child classes ...
pass
class PersonTypeSerializer(TypeBaseSerializer, serializers.ModelSerializer):
class Meta:
model = PersonType
fields = TypeBaseSerializer.Meta.fields + ['another_field']
class CompanyTypeSerializer(TypeBaseSerializer, serializers.ModelSerializer):
class Meta:
model = CompanyType
fields = TypeBaseSerializer.Meta.fields + ['some_other_field']
So now since the fields name and id are declared on the parent class (TypeBaseSerializer), they will be available on PersonTypeSerializer and since this is a child class of ModelSerializer those fields will be populated from the model instance.
You can also use SerializerMethodField on the TypeBaseSerializer, even though it is not a ModelSerializer.
class TypeBaseSerializer(serializers.Serializer):
# you will have to re-declare fields here since this is not a ModelSerializer
name = serializers.CharField()
id = serializers.CharField()
other_field = serializers.SerializerMethodField()
class Meta:
fields = ['id', 'name', 'other_field']
def get_other_field(self, instance):
# will be available on child classes, which are children of ModelSerializers
return instance.other_field
Just iterating a bit over #adki's answer:
it is possible to skip model for TypeBaseSerializer;
derived serializers can refer to TypeBaseSerializer.Meta, so you would change them in a single place.
class TypeBaseSerializer(serializers.Serializer):
class Meta:
fields = ('id', 'name', 'created')
abstract = True
def func(...):
# ... some logic
class PersonTypeSerializer(TypeBaseSerializer):
class Meta:
model = PersonType
fields = TypeBaseSerializer.Meta.fields + ('age', 'date_of_birth')
class CompanyTypeSerializer(TypeBaseSerializer):
class Meta:
model = CompanyType
fields = TypeBaseSerializer.Meta.fields
I have defined a serializer like this:
class ActivitySerializer(serializers.ModelSerializer):
activity_project = serializers.SlugRelatedField(queryset=Project.objects.all(), slug_field='project_name')
activity_tags = serializers.SlugRelatedField(queryset=Tag.objects.all(), slug_field='tag_name', many=True)
class Meta:
model = Activity
fields = ('activity_name', 'activity_description', 'activity_status', 'activity_completion_percent', 'activity_due_date', 'activity_project', 'activity_tags',)
Now if I insert an activity_tag that does not exist in the database, I get a validation error"
{
"activity_tags": [
"Object with tag_name=test does not exist."
]
}
I would like to create a validation method that adds the tag in the database if it does not exist.
I have tried using the
def validate(self, attrs):
....
method, but apparently for a slug field there is a method that is called before this one.
Can someone point me to the right method I should use? Would this method be called in the corresponding view?
I think you would need to create a nested serializer for this to work. This is totally untested and off the top of my head, but maybe something like this:
class ActivityTagFieldSerializer(serializer.ModelSerializer):
tag_name = serializers.SlugField()
class Meta:
model = Tag
fields = ('tag_name')
class ActivitySerializer(serializer.ModelSerializer):
activity_tags = ActivityTagFieldSerializer(many=True)
class Meta:
model = Activity
fields = ('activity_tags', 'activity_project', ...)
def create(self, validated_data):
tags = validated_data.pop('activity_tags')
activity = Activity.objects.create(**validated_data)
for tag in tags:
try:
tag_to_add = Tag.objects.get(**tag)
except:
tag_to_add = Tag.objects.create(**tag)
activity.activity_tags.add(tag_to_add)
return activity
Check the API guide for writable nested serializers
I managed to do this by subclassing SlugRelatedField and overriding "to_internal_value" method. In the original implementation this method tries to get an object from the queryset, and if an object doesn't exist it fails the validation. So instead of calling "get" method, I'm calling "get_or_create":
class CustomSlugRelatedField(serializers.SlugRelatedField):
def to_internal_value(self, data):
try:
obj, created = self.get_queryset().get_or_create(**{self.slug_field: data})
return obj
except (TypeError, ValueError):
self.fail('invalid')