I have 2 models
class Parent(models.Model):
name = models.CharField(max_length=50)
class Child(models.Model):
parent = models.ForeignKey(Parent,related_name='child')
child_name = models.CharField(max_length=80)
type = models.BooleanField()
I want to fetch result from parent model and related records from child
Parent.objects.all()
it returns me all records form parent and child IN django rest framework but I want only that child which type is ture, how can i add condition
Please let me know
In your Parent generic list api view override the get_queryset method:
def get_queryset(self):
return (Parent.objects.all()
.prefetch_related(Prefetch('child', queryset=Child.objects.filter(type=True))))
Also on a side note I suggest you not to name the field type on child model since it conflicts with the python keyword type. And another suggestion is to use the related_name value as children.
Related
I am using a model that consists of many fields. There is one field that is a property, and it returns an instance of a model. Something like the following:
class A(Model):
#property
def last_obj(self):
# Returns an object
The issue I'm having is that this property can return 2 different Model types. It can either return an object of type one, or an object of type two. This creates complications in the serializer. I have a serializer that consists of nested serializers. The two objects are similar enough that one serializer can be used over the other, but then the fields unique to them are not serialized.
class A_Serializer(Serializer):
class SerializerOne(CustomSerializer):
#Serializes certain fields in custom manner
class Meta:
model = models.one
exclude = ('id')
base_name = 'one'
class SerializerTwo(CustomSerializer):
#Serializes certain fields in custom manner
class Meta:
model = models.two
exclude = ('id')
base_name = 'two'
last_obj = SerializerOne() #This works, but not viable because of what I stated above
So my solution to be able to dynamically call the correct serializer, was to conditionally serialize the property within a serializer method field:
class A_Serializer(Serializer):
class SerializerOne(CustomSerializer):
#Serializes certain fields in custom manner
class Meta:
model = models.one
exclude = ('id')
base_name = 'one'
class SerializerTwo(CustomSerializer):
#Serializes certain fields in custom manner
class Meta:
model = models.two
exclude = ('id')
base_name = 'two'
def get_last_obj(self, instance):
if (isinstance(instance.last_obj, models.one)):
return self.SerializerOne(instance.last_obj).data
else:
return self.SerializerTwo(instance.last_obj).data
last_obj = SerializerMethodField() #Does not work
However, this solution creates the error "NoneType Object is not iterable" and it happens at
super(ReturnDict, self).__init__(*args, **kwargs) in rest_framework/utils/serializers_helpers.py in init which causes the error at return ReturnDict(ret, serializer=self) in rest_framework/serializers.py in data
I do not understand why calling a nested serializer like obj = Serializer() works, but calling the serializer explicitly like obj = Serializer(instance).data does not work in this situation. Can anyone figure out what I have been doing wrong? Thank you.
I have found out from here that when working with hyperlinked relations (which in my case was the CustomSerializer that SerializerOne and SerializerTwo were inheriting from), you must pass the request object through context. The reason why obj = Serializer() works, but obj = Serializer(instance).data does not work is that in the former, the request object is automatically added through context through DRF. While in the latter, it is being explicitly called so you must pass context with the request object manually. So for me to get it working, I did:
return self.SerializerOne(instance.last_obj, context={'request': self.context['request']}).data
inside the serializer method field.
I've implemented graphql and I'm migrating to relay. I already have a uuid for every table and that is named 'id'. And my application I found this github thread that talks about possibly changing the spec but it feels like a rabbit hole.
Is there a simple way that I can use my own custom id with relay?
If you've already implemented a default relay endpoint then you should have some
TableNameNode classes that have a Meta nested class, and a seperate Query
class.
class ExampleTableNameNode(DjangoObjectType):
class Meta:
model = ExampleTableName
interface = (relay.Node,)
class Query(object):
example_table_name = relay.Node.Field(ExampleTableNameNode)
all_example_table_names = DjangoFilterConnectionField(ExampleTableNameNode)
def resolve_example_table_name(self, info, **kwargs):
pass
def resolve_all_example_table_names(self, info, **kwargs):
pass
The interface = (relay.Node,) is what defines:
How the ids are being generated
How they are used to fetch data
If we create a relay.Node subclass that redefines these two features then we can use our custom ids.
class CustomNode(relay.Node):
class Meta:
name = 'Node'
#staticmethod
def to_global_id(type, id):
#returns a non-encoded ID
return id
#staticmethod
def get_node_from_global_id(info, global_id, only_type=None):
model = getattr(Query,info.field_name).field_type._meta.model
return model.objects.get(id=global_id)
Here we implemented two functions, to_global_id, and get_node_from_global_id.
The line model = ... is a bit of magic to go from the graphql query table name
to the actual model. If that doesn't work you'll just need to make a dictionary
to go from something like example_table_name to the actual ExampleTableName
django model.
Once you do that you'll have to replace the two references to relay.Node with
CustomNode like so.
class ExampleTableNameNode(DjangoObjectType):
class Meta:
model = ExampleTableName
interface = (CustomNode,)
class Query(object):
example_table_name = CustomNode.Field(ExampleTableNameNode)
all_example_table_names = DjangoFilterConnectionField(ExampleTableNameNode)
def resolve_example_table_name(self, info, **kwargs):
pass
def resolve_all_example_table_names(self, info, **kwargs):
pass
The answer is in the graphene docs. I read them when I was implementing
graphene and relay but there is so much to learn at once that it's easy to read
through custom node section and not remember later that you need to do a custom
node solution.
I have two related models and serializers for both of them. When I am serializing one of these models (the serializer has a depth of 1) the result includes some fields from the related object that should't be visible. How an I specify which serializer to use for the relation? Or is there anyway to tell Rest Framework to exclude some fields from the related object?
Thank you,
I think one way would be to create an extra serializer for the model where you want to return only limited number of fields and then use this serializer in the serializer of the other model. Something like this:
class MyModelSerializerLimited(serializers.ModelSerializer):
class Meta:
model = MyModel
fields = ('field1', 'field2') #fields that you want to display
Then in the other serializer use the MyModelSerializerLimited:
class OtherModelSerializer(serializers.ModelSerializer):
myfield = MyModelSerializerLimited()
class Meta:
model = OtherModel
fields = ('myfield', ...)
depth = 1
You could override restore_fields method on serializer. Here in restore_fields method you can modify list of fields - serializer.fields - pop, push or modify any of the fields.
eg: Field workspace is read_only when action is not 'create'
class MyPostSerializer(ModelSerializer):
def restore_fields(self, data, files):
if (self.context.get('view').action != 'create'):
self.fields.get('workspace').read_only=True
return super(MyPostSerializer, self).restore_fields(data, files)
class Meta:
model = MyPost
fields = ('id', 'name', 'workspace')
Let's say I have this simple model :
class BlogPost(models.Model):
author = models.ForeignKey(MyUser)
body = models.TextField()
title = models.CharField(max_length=64)
urlid = models.CharField(max_length=32)
private_data = models.CharField(max_length=64)
private_data contains data that I do not want to expose to the API (!). I'm using a ModelSerializer :
class BlogPostSerializer(serializers.ModelSerializer):
class Meta:
model = BlogPost
def __init__(self, *args, **kwargs):
# Don't pass the 'request' arg up to the superclass
request = kwargs.pop('request', None)
# Instatiate the superclass normally
super(ModelSerializer, self).__init__(*args, **kwargs)
self.request = request
def absolute_url(self, blogpost):
return blogpost.get_absolute_url(self.request)
The absolute_url method needs the request to determine the domain name (dev or prod for example) and if it was made in http or https.
I want to specify which fields in the model are going to get returned by the serializer (not expose private_data for example). Simple enough:
class BlogPostSerializer(serializers.ModelSerializer):
class Meta:
model = BlogPost
fields = ('author', 'body', 'title', 'urlid',)
# The same jazz after that
All right, it works. Now I also want to return absoluteUrl:
class BlogPostSerializer(serializers.ModelSerializer):
absoluteUrl = serializers.SerializerMethodField('absolute_url')
class Meta:
model = BlogPost
fields = ('author', 'body', 'title', 'urlid',)
# The same jazz after that
Well, without surprises, this returns only the fields I specified, without the absoluteUrl. How can I return only certain fields of the model AND the absoluteUrl, calculated from the serializer?
If I don't specify fields I do get the absoluteUrl, but with all the model's fields (including private_data). If I add 'absoluteUrl' to fields I get an error because blogpost.absoluteUrl doesn't exist (no surprises there). I don't think I could use this method http://django-rest-framework.org/api-guide/serializers.html#specifying-fields-explicitly because I need the request to obtain the absoluteUrl (or can I specify arguments to the model's method ?)
If I don't specify fields I do get the absoluteUrl, but with all the model's fields (including private_data). If I add 'absoluteUrl' to fields I get an error because blogpost.absoluteUrl doesn't exist (no surprises there).
You should just be adding 'absoluteUrl' to the fields tuple, and it should work just fine - so what error are you seeing?
The absolute_url method needs the request to determine the domain name (dev or prod for example) and if it was made in http or https.
Note that you can also pass through context to the serializer without modfiying the __init__, just pass a context={'request': request} when instantiating the serializer. The default set of generic views do this for you, so you can access self.context['request'] in any of the serializer methods. (Note that this is how hyperlinked relationships are able to return fully qualified URLs)
I'm trying to create a new Topic and the category id is dynamically determined in javascript on the client side. The problem i'm having is I pass the category id and I want to lookup the correct category object, but using a model form, it checks if the category is an instance of Category before I can assign it and save it.
--model.py--
class Topic(models.Model):
category = models.ForeignKey(Category)
--form.py--
class TopicForm(ModelForm):
category = forms.IntegerField(widget=forms.HiddenInput())
class Meta:
model = Topic
fields = ('category')
--view.py--
form = TopicForm(request.POST)
if form.is_valid():
form.save(commit=False) # throws exception category is not a Category instance
form.category = Category.objects.get(pk=form.cleaned_data.get('category'))
form.save()
Use a ModelChoiceField instead of the IntegerField in your form. See the built-in fields reference
Following Oggy's suggestion, I changed it to a ModelChoiceField and now Django does all the magic behind the scenes.
category = forms.ModelChoiceField(Category.objects.all(), widget=forms.HiddenInput())
Now I hope the queryset doesn't get evaluated, since it's not necessary and there are 90,000 records. :)