When using the HyperlinkedModelSerializer from Django REST Framework, the field id is not included in the fields by default. This question has an answer that explains that well.
However I have a problem I'd like to solve in a particular way.
I have a model with custom ID and few dozens of other fields:
class Foo(models.Model):
id = models.IntegerField(primary_key=True)
# 20-30 fields
In the serializers.py I'd like to include all fields from the model:
class FooSerializer(serializers.HyperlinkedModelSerializer):
class Meta:
model = Foo
fields = '__all__'
However this doesn't include the field id. Defining id = serializers.ReadOnlyField() doesn't help me either, as id shoud be editable.
Specifying all the fields manually like this:
fields = ('id', # all other fields)
would be a solution I'm trying to circumvent because the model class has a lot of fields and they might change in future.
Is there an elegant possibility to add the field id? Maybe overriding the __init__ method?
Add id attribute in FooSerializer serializer as:
class FooSerializer(serializers.HyperlinkedModelSerializer):
id = serializers.IntegerField(read_only=True)
class Meta:
model = Foo
fields = '__all__'
You can create your custom HyperlinkedModelSerializer and override get_default_field_names to include the id like normal ModelSerializer does.
Example:
class CustomHyperlinkedModelSerializer(HyperlinkedModelSerializer ):
def get_default_field_names(self, declared_fields, model_info):
return (
[model_info.pk.name] +
[self.url_field_name] +
list(declared_fields) +
list(model_info.fields) +
list(model_info.forward_relations)
)
Note : this is just an idea. I have not tested it yet.
HyperlinkedModelSerializer doesn't include the id field by default. You can include id by adding it to the serializer as an attribute like this:
class FooSerializer(serializers.HyperlinkedModelSerializer):
id = serializers.IntegerField()
class Meta:
model = Foo
fields = '__all__'
Related
The model:
class Item(models.Model):
company = models.ForeignKey(Company, on_delete=models.CASCADE)
item_num = models.IntegerField()
# other fields...
class Meta:
unique_together = [('company', 'item_num') ]
Serializer:
class ItemSerializer(serializers.ModelSerializer):
class Meta:
model = Item
fields = ('company_id', 'item_num', )
The problem is that django rest framework generates a ReadOnlyField() for the company_id field, so this field is not editable when I create a new instance in view code like this:
s = ItemSerializer(data=request.POST)
s.save()
I also lose the default UniqueTogetherValidator that is defined in the model.
Though, if I change the serializer field name from 'company_id' to 'company', I do get the validator, as drf will generate PrimaryKeyRelatedField so it will be editable.
How can I still name my foreign key objects like 'company_id', because I do prefer naming them like this, and still get the default validation and saving behavior? Preferably without adding to much code to the serializer.
company_id is a read-only field because it lacks a proper definition in the Model for the serializer to understand it.
Steps to get it working:
Add an explicit field definition
Add the constraint
Serializer would be:
class ItemSerializer(serializers.ModelSerializer):
company_id = serializers.PrimaryKeyRelatedField(source=company, queryset=Company.objects.all())
class Meta:
model = Item
fields = ('company_id', 'item_num', )
validators = [
UniqueTogetherValidator(
queryset=Item.objects.all(),
fields=('company_id', 'item_num')
)
]
I can't seem to work out how to hook into the queryset of a readonly field in Django admin. In particular I want to do this for an inline admin.
# models.py
class Value(models.Model):
name = models.TextField()
class AnotherModel(models.Model):
values = models.ManyToManyField(Value)
class Model(models.Model):
another_model = models.ForeignKey(AnotherModel)
# admin.py
class AnotherModelInline(admin.TabularInline):
# How do I order values by 'name'?
readonly_fields = ('values',)
class ModelAdmin(admin.ModelAdmin):
inlines = (AnotherModelInline,)
Note that this could probably be done by overriding the form and then setting the widget to disabled, but that's a bit of a hack and doesn't look nice (I don't want greyed out multi-select, but a comma-separated list of words.
You can set an ordering metadata in the Values model:
class Value(models.Model):
name = models.TextField()
class Meta:
ordering = ['name']
This is my Model:
class Post(models.Model):
user = models.ForeignKey(User)
post = models.CharField(max_length=400)
country = models.ForeignKey(Country, blank=True, null=True)
and this is my serializer:
class PostSerializer(serializers.ModelSerializer):
class Meta:
model = Post
fields = ('user', 'post', 'country',)
def create(self, validated_data):
post = Post(
user = User.objects.get(username='MyUser'),
post = validated_data['post'],
)
if validated_data.get('country', None):
post.country = validated_data['country']
return post
Is there any way for me to tell DRF that if the value of the field is null (because the 'country' field is optional and sometimes not provided) then to skip it and just serialize the other data? Or at least serialize it with a value of None?
I don't think I can use SerializerMethodField (http://www.django-rest-framework.org/api-guide/fields/#serializermethodfield) because the 'country' field is not a read-only field (I write too it too, if it is provided).
I basically want to omit the field (or at least make the value None) when serializing an object If the field is null.
As of DRF 3.2.4, so long as you add
blank=True
to the models field like so:
class Post(models.Model):
country = models.ForeignKey(Country, blank=True)
then DRF will treat the field as optional when serializing and deserializing it (Note though that if there is no null=True on the model field, then Django will raise an error if you try to save an object to the database without providing the field).
See the answer here for more information: DjangoRestFramework - correct way to add "required = false" to a ModelSerializer field?
If you are using pre-DRF 3.2.4, then you can override the field in the serializer and add required=False to it. See the documentation here for more information on specifying or overriding fields explicitily: http://www.django-rest-framework.org/api-guide/serializers/#specifying-fields-explicitly
So something like this (Note that I did not fully test the code below but it should be something along these lines):
class PostSerializer(serializers.ModelSerializer):
country = serializers.PrimaryKeyRelatedField(required=False)
class Meta:
model = Post
fields = ('user', 'post', 'country',)
This thread might be useful:
https://stackoverflow.com/a/28870066/4698253
It basically says that you can override the to_representation() function with a slight modification.
I would have put this in the comments but I don't have enough points yet :(
Use allow_null=True:
allow_null - If set to True, the field will accept values of None or the empty string for nullable relationships. Defaults to False.
serializers.py
class PostSerializer(serializers.ModelSerializer):
tracks = serializers.PrimaryKeyRelatedField(allow_blank=True)
class Meta:
model = Post
models.py:
class Car():
producer = models.ForeignKey(Producer, blank=True, null=True,)
color = models.CharField()
car_model = models.CharField()
doors = models.CharField()
serializers.py:
class CarSerializer(ModelSerializer):
class Meta:
model = Car
fields = Car._meta.get_all_field_names()
So, here I want to use all fields. But I have an error:
Field name producer_id is not valid for model Car.
How to fix that?
Thanks!
According to the Django REST Framework's Documentation on ModelSerializers:
By default, all the model fields on the class will be mapped to a corresponding serializer fields.
This is different than Django's ModelForms, which requires you to specify the special attribute '__all__' to utilize all model fields. Therefore, all that is necessary is to declare the model.
class CarSerializer(ModelSerializer):
class Meta:
model = Car
Update (for versions >= 3.5)
The behaviour described above was deprecated in version 3.3, and forbidden since version 3.5.
It is now mandatory to use the special attribute '__all__' to use all fields in the Django REST Framework, same as Django Forms:
Failing to set either fields or exclude raised a pending deprecation warning in version 3.3 and raised a deprecation warning in 3.4. Its usage is now mandatory.
So now it must be:
class CarSerializer(ModelSerializer):
class Meta:
model = Car
fields = '__all__'
You could use fields = '__all__' to get all your fields or you could specify if you want a limited number of fields to be returned. See documentation.
But this returns the id value for the foreign key field i.e. producer in your case. To get all the fields for producer, you need to create a serializer class for that too. See here.
So your updated serializers.py should be:
class ProducerSerializer(ModelSerializer):
class Meta:
model = Producer
class CarSerializer(ModelSerializer):
producer= ProducerSerializer(read_only=True)
class Meta:
model = Car
fields = ('producer', 'color', 'car_model', 'doors', )
if you want all fields to be included in the serializer you can use fields = '__all__':
class CarSerializer(serializer.ModelSerializer):
class Meta:
fields = '__all__'
model = Car
But this approach is not recommended. We should always explicitly specify all fields. This is because it gives us control over fields displayed. If we don't want a field's data to be displayed, we can avoid that.
class CarSerializer(serializer.ModelSerializer):
class Meta:
fields = ['name', 'color', 'company', 'price', ]
model = Car
Before posting this question I've read few questions on SOF. but they are from 2012 and very confusing as well.
for e.g Django Rest Framework - Get related model field in serializer
my question is very straight forward
models.py
class User(models.Model):
username = models.CharField(max_length=100,unique=True)
password = models.CharField(max_length=100,null=False,blank=False)
class Car(models.Model):
user = models.ForeignKey(User)
car_name = models.CharField(max_length=100,null=True,blank=True)
serializers.py
class UserSerializer(serializers.ModelSerializer):
class Meta:
model = User
fields = ('username','password' )
class CarSerializer(serializers.ModelSerializer):
#user = ?? what should I write or is there any better approach for serializing Car objects
class Meta:
model = Car
fields = ('user','car_name')
views.py
class UserViewSet(viewsets.ModelViewSet):
queryset = User.objects.all()
serializer_class = UserSerializer
class CarViewSet(viewsets.ModelViewSet):
queryset = Car.objects.all()
serializer_class = CarSerializer
Please suggest all possible approaches.
1 more query. which one is better ModelSerializer or HyperlinkModelSerializer. as I saw different different answers containing these two.
You just need to do:
class CarSerializer(serializers.ModelSerializer):
user = UserSerializer()
class Meta:
model = Car
fields = ('user','car_name')
that is all.
Also, you should take a look to the kindnesses of serializers.Field and serializers.SerializerMethodField, you can play with them and customize your response data as much as you wish.
As to the question around HyperlinkedModelSerializer-ModelSerializer, very clear here:
The HyperlinkedModelSerializer has the following differences from ModelSerializer:
It does not include the pk field by default.
It includes a url field, using HyperlinkedIdentityField.
Relationships use HyperlinkedRelatedField, instead of PrimaryKeyRelatedField.
Hope that helps.