I'm learning and new to Django Rest Framework and I'm having an issue in serializer validations and ListSerializer update method.
I have an APIView class which handles the put request. I just wanted to have a custom validation and so I've overridden validate method in the serializer class.
From postman I'm sending a JSON data to this APIView Class.
Sample JASON data:
[
{
"id": 1,
"ip": "10.1.1.1",
"host_name": "hostname 1"
},
{
"id": 2,
"ip": "10.1.1.2",
"host_name": "hostname 2"
}
]
When I receive the data and do serializer.is_valid() it passes the flow to the overridden validate function. But in there when I check for the attrs argument, I get all the fields except the id. The key and value for id are not present. It shows None.
The same issue occurred to me when I was trying to override the update method in ListSerializer.
when I tried the below code in the ListSerializer's update method,
data_mapping = {item['id']: item for item in validated_data}
I got an error saying KeyError 'id'.
It seems it's not accepting id field and I'm not sure why! Please, someone explain this to me if I'm wrong anywhere.
Serializer class
from rest_framework import serializers
from .models import NoAccessDetails
class NoAccessDetailsListSerializer(serializers.ListSerializer):
def update(self, instance, validated_data)
data_mapping = {data.id: data for data in instance}
#Here I'm getting KeyError ID
validated_data_mapping = {item['id']: item for item in validated_data}
return
class NoAccessDetailsSerializer(serializers.ModelSerializer):
class Meta:
model = NoAccessDetails
list_serializer_class = NoAccessDetailsListSerializer
fields = ("id", "ip", "host_name")
def validate(self, data):
id_val = data.get('id')
ip = data.get('ip')
host_name = data.get('host_name')
#here the id value is None
print('id val {} '.format(id_val))
return data
If I am understanding correctly, the issue is that you do not see the id field inside of validated_data. If so, I believe this is intentional in the framework:
https://github.com/encode/django-rest-framework/issues/2320
Basically, the id field is read_only by default. Let me know if you have questions that are not answered by Tom's response to that issue.
EDIT: Also feel free to share the higher level use case (what you are planning on doing with the ID inside of validation), and maybe we can offer alternative approaches.
Related
I'm not very familiar with DRF and I haven't found a solution on google for this problem (most answers are about a model with a field as enum, my problem is different)
You see, we have an Enum in a Django application. Let's call it SomeValuesEnum.
class SomeValuesEnum(Enum):
ONE_VALUE = "One value"
ANOTHER_VALUE = "Another value"
What I need to do is to create a GET endpoint that returns the following
{
"count": 2,
"page_count": 1,
"next": null,
"previous": null,
"results": [
{
"value": "One value",
"name": "ONE_VALUE"
}, {
"value": "Another value",
"name": "ANOTHER_VALUE"
}
]
}
I know I need to create a serializer, but I haven't been able to create one and "feed it".
For example, I started with something like this:
class SomeValueSerializer(serializers.Serializer):
Meta:
model = SomeValuesEnum,
fields = '__all__'
and on the view:
class SomeValueListView(APIView):
serializer_class = SomeValueSerializer
def get(self, request):
choices = [{"value": target.value, "name": target.value.capitalize()} for target in SomeValuesEnum]
serializer = SomeValueSerializer(data=choices)
return Response(status=status.HTTP_200_OK, data=serializer.data)
I also tried this
class IncidentSerializer(serializers.Serializer):
name = serializers.CharField(required=False, allow_blank=True, max_length=100)
value = serializers.CharField(required=False, allow_blank=True, max_length=100)
I'm not sure if I'm failing on the creation of the serializer, or in how I invoke him on the view (or maybe both)
Any guidance on the right direction will be greatly appreciate it.
An enum is not a django model. You can have a DRF serializer for something that isn't a model, but you shouldn't give it a model field of something that isn't a model.
See here: Declaring Serializers
Not here: Model Serializers
Furthermore, you are creating a class-based view here:
SomeValueListView(APIView)
You don't necessarily need this, you could use a function based view, which may be easier for you to understand given you are new to DRF. I only say function based views are easier to understand since there isn't so much built in functionality. This can make it easier to debug for someone new to DRF. You can still use the serializer by calling it directly in the view.
See here: Function Based Views
And here: Serializing Objects
Finally...given this code:
choices = [{"value": target.value, "name": target.value.capitalize()} for target in SomeValuesEnum]
I am making the assumption that there could be multiple distinct objects going into this serializer, given that you are using a list comprehension. Either you need to call the serializer separately for each object in the array, or you call the serializer with (many=True). Pretty sure this is your main issue. Like this:
serializer = SomeValueSerializer(data=choices, many=True)
See here: Dealing with multiple objects
Also, in my experience it is better to parse incoming data to the serializer within the serializer itself, not in the view. To me it is a separation of concerns issue, but other people may feel differently. This would look something like this:
class SomeValueListView(APIView):
serializer_class = SomeValueSerializer
def get(self, request):
serializer = SomeValueSerializer(data=SomeValuesEnum)
return Response(status=status.HTTP_200_OK, data=serializer.data)
class SomeValueSerializer(serializer.Serializer):
def to_internal_value(self, data)
name = data.value.capitalize()
value = data.value
return {
'name': name,
'value': value,
}
I'm using django with mongoengine and mongoengine-rest-framework.
As shown in this article, specifying related_model_validations field in Meta class of a Serializer
class Comment(Document):
post = ReferenceField(Post)
owner = ReferenceField(User)
text = StringField(max_length=140)
isApproved = BooleanField(default=False)
from rest_framework_mongoengine import mongoengine_serializer
class CommentSerializer(MongoEngineModelSerializer):
class Meta:
model = Comment
depth = 1
related_model_validations = {'owner': User, 'post': Post}
exclude = ('isApproved',)
can help to achieve the following result if the document referenced by the ReferenceField is missing:
{
"owner":["User with PK ... does not exist."]
}
So instead of raising a validation exception, json is modified.
However, this article is written for the old version of mongoengine-rest-framework and in the current version there is no field related_model_validations in Serializer Meta class.
So how to achieve the similar result in the current version of the mongoengine-rest-framework?
Sorry for late response, Aleksei.
Currently, if you want to PUT or POST a comment JSON, you just pass existing owner and post as their ids like:
{
post: 2,
user: aleksei.rozhnov#stackoverflow.com,
text: "Contrary to the popular belief, Karl Marx and Friedrich Engels are not a couple, but four different people"
}
So, if you want to update Comment, Post and Author at the same time, I'm afraid, that's not possible.
In GET requests you can get related fields as nested sub-JSONs with non-zero depth argument to Serializer, as you did it in your example.
I have a setup where I need to write an API for an existing javascript datamodels which i do not want to touch (for now). The javascript data has a different architecture than I want to have on the server. So my goal is to transform the data that I get from javascript to fit my database model when data is sent to the API. When data is requested from the API, it should match the expected data model of javascript.
I wonder if I can do that with ModelSerializers, if yes, where is the right place to transform the data? In the view? In the serializer.
My setup is like so:
//javascript structure
{
scores: [
{
id: 12,
points: 2
maxpoints: 12
siteuxid: 'EXAMPLE'
},
{ ... }
]
}
//More models in django
{
scores: [
{
id: 12,
points: 2,
question: {
id: 12,
maxpoints: 12,
siteuxid: 'EXAMPLE'
}
},
]
}
Are there any examples anyone can point me to, that achive the same? Basically it is all about having different data structures in server and client and making them compatible. Googleing did not help.
EDIT:
My first problem is that I do not get all posted data in my Serializer. When I post
{
"scores": [{"id":"QFELD_1.1.3.QF2","siteuxid":"VBKM01_VariablenTerme","section":1,"maxpoints":4,"intest":false,"uxid":"ER2","points":0,"value":0,"rawinput":"363"}]
}
to
class UserDataSerializer(serializers.ModelSerializer):
scores = ScoreSerializer(many=True, required=False)
def create(self, validated_data):
print('userDataSerializer validated_data', validated_data)
...
class ScoreSerializer(serializers.ModelSerializer):
id = serializers.CharField(required=False, allow_blank=True, max_length=100)
question = QuestionSerializer(required=False)
class Meta:
model = Score
fields = ('id', 'question', 'points', 'value', 'rawinput', 'state')
I only get the output
userDataSerializer validated_data {'scores': [OrderedDict([('id', 'QFELD_1.1.3.QF2'), ('points', 0), ('value', 0), ('rawinput', '363')])]}
without the score.maxpoints and so on (as it is not in the serializer, but how can I add it? To validated data in order to create a proper question object from the posted data in UserDataSerializer)
The answer is yes, you will use the view to modify your input data, as you must do these tweaks in your data before the view sends the data to the serializers. This is due to the same reason that you only see the attributes of your serializer in your validated data - the serializer ignores all the attributes it does not recognize.
So, first of all, change request.data in your view's post method to make it structured as you need.
def post(self, request, *args, **kwargs):
request.data['question'] = {
'maxpoints': request.data.pop('maxpoints'),
'siteuxid': request.data.pop('siteuxid'),
}
This should be all you need to get started.
However, note that it's strange that question has id: 12 in your example. If you are trying to create a question object along with your score object, it should have no id. If the question is an existing object, though, you should not be sending a dict, but only the id instead.
For example, you should send question: 1 in your input. DRF's ModelSerializer is smart enough to know that the score you are trying to save is to be related with the question which has id = 1. While you're at it, inspect the serializer's validated_data and you'll see the instance of question with id = 1. Magic!
I am a bit frustrated with this problem using the Django Rest Framework:
I am using a viewset, with a custom serializer. This serializer has its depth set to 1. When i query this viewset I get the correct representation of data for example:
data = {
id: 1,
issue_name: 'This is a problem',
status: {
id: 3,
name: 'todo'
}
}
The problem comes in when I need to update the status. For example if I want to select another status for this issue, for example:
status_new = {
id: 4,
name: 'done'
}
I send the following PATCH back to the server, this is the output:
data = {
id: 1,
issue_name: 'This is a problem',
status: {
id: 4,
name: 'done'
}
}
However, the status does not get updated. Infact, it is not even a part of the validated_data dictionary. I have read that nested relations are read-only. Could someone please tell me what I need to do this in a simple way?
Would really be obliged.
Thanks in advance
As stated in the documentation, you will need to write your own create() and update() methods in your serializer to support writable nested data.
You will also need to explicitly add the status field instead of using the depth argument otherwise I believe it won't be automatically added to validated_data.
EDIT: Maybe I was a bit short on the details: what you want to do is override update in ModelIssueSerializer. This will basically intercept the PATCH/PUT requests on the serializer level. Then get the new status and assign it to the instance like this:
class StatusSerializer(serializers.ModelSerializer):
class Meta:
model = Status
class ModelIssueSerializer(serializers.ModelSerializer):
status = StatusSerializer()
# ...
def update(self, instance, validated_data):
status = validated_data.pop('status')
instance.status_id = status.id
# ... plus any other fields you may want to update
return instance
The reason I mentioned in the comment that you might need to add a StatusSerializer field is for getting status into validated_data. If I remember correctly, if you only use depth then nested objects might not get serialized inside the update() / create() methods (although I might be mistaken on that). In any case, adding the StatusSerializer field is just the explicit form of using depth=1
I usually use custom field for such cases.
class StatusField(serializers.Field):
def to_representation(self, value):
return StatusSerializer(value).data
def to_internal_value(self, data):
try:
return Status.objects.filter(id=data['id']).first()
except (AttributeError, KeyError):
pass
And then in main serializer:
class IssueSerializer(serializers.ModelSerializer):
status = StatusField()
class Meta:
model = MyIssueModel
fields = (
'issue_name',
'status',
)
I would assume that your models mimic your serializer's data. Also, I would assume that you have a one to many relation with the status(es) but you don't need to create them via the issue serializer, you have a different endpoint for that. In such a case, you might get away with a SlugRelatedField.
from rest_framework import serializers
class StatusSerializer(serializers.ModelSerializer):
class Meta:
model = MyStatusModel
fields = (
'id',
'status',
)
class IssueSerializer(serializers.ModelSerializer):
status = serializers.SlugRelatedField(slug_field='status', queryset=MyStatusModel.objects.all())
class Meta:
model = MyIssueModel
fields = (
'issue_name',
'status',
)
Another valid solution would be to leave here the foreign key value and deal with the display name on the front-end, via a ui-select or select2 component - the RESTfull approach: you are handling Issue objects which have references to Status objects. In an Angular front-end app, you would query all the statuses from the back-end on a specific route and then you will display the proper descriptive name based on the foreign key value form Issue.
Let me know how is this working out for you.
I would like to share django model history (created by django-simple-history) using tastypie.
Problem is, how to prepare ModelResource for this purpose.
Access to model history is by model.history manager. So access to all changes of model we can gain by model.history.all()
What i would like to obtain? For example. I have django model Task and the API endpoints:
http://127.0.0.1/api/v1/task - display all tasks list
http://127.0.0.1/api/v1/task/1 - display details for choosen task
http://127.0.0.1/api/v1/task/1/history - display history of task no. 1
First two links presents default behavior of ModelResource. what i have till now?
class TaskResource(ModelResource):
class Meta:
# it displays all available history entries for all task objects
queryset = Task.history.all()
resource_name = 'task'
def prepend_urls(self):
return [
url(r"^(?P<resource_name>%s)/(?P<pk>\w[\w/-]*)/history$" % (self._meta.resource_name,),
self.wrap_view('get_history'),
name="api_history"),
]
def get_history(self, request, **kwargs):
#...
get_history should return bundle with history entries.. but how this method should look?
I guess, i need to create bundle with needed data, but don't know how exactly should i do that.
Does someeone have experience with simple-history and tastypie to present some simple example?
It seems, solution was simpler than i thought. Maybe someone use this in feature:
class TaskHistoryResource(ModelResource):
class Meta:
queryset = Task.history.all()
filtering = { 'id' = ALL }
class TaskResource(ModelResource):
history = fields.ToManyField(AssetTypeHistoryResource, 'history')
class Meta:
# it displays all available history entries for all task objects
queryset = Task.history.all()
resource_name = 'task'
def prepend_urls(self):
return [
url(r"^(?P<resource_name>%s)/(?P<pk>\w[\w/-]*)/history$" %(self._meta.resource_name,),
self.wrap_view('get_history'),
name="api_history"),
]
def get_history(self, request, **kwargs):
try:
bundle = self.build_bundle(data={'pk': kwargs['pk']}, request=request)
obj = self.cached_obj_get(bundle=bundle, **self.remove_api_resource_names(kwargs))
except ObjectDoesNotExist:
return HttpGone()
except MultipleObjectsReturned:
return HttpMultipleChoices("More than one resource is found at this URI.")
history_resource = TaskHistoryResource()
return history_resource.get_list(request, id=obj.pk)
A bit changed solution from:
http://django-tastypie.readthedocs.org/en/latest/cookbook.html#nested-resources
Basically, there was need to create additional resource with history entries. get_history method creates and returns instance of it with appropriate filter on id field (in django-simple-history id field contain id of major object. Revision primary key names history_id)
Hope, that will help someone.