Die Methode `.create()` unterstützt standardmäßig schreibgeschützte Felder nicht.

Question

Ich habe ein großes Problem in Bezug auf die Serialisierung einer Viele-zu-viele-Beziehung mit Zwischenmodell in DRF: Wenn die Anfrage-Methode ist, funktioniert alles perfekt. Aber sobald ich versuche, Daten POST oder PUT an dem API ich die folgende Fehlermeldung erhalten:

Traceback (most recent call last): 
    File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/django/core/handlers/base.py", line 149, in get_response 
    response = self.process_exception_by_middleware(e, request) 
    File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/django/core/handlers/base.py", line 147, in get_response 
    response = wrapped_callback(request, *callback_args, **callback_kwargs) 
    File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/django/views/decorators/csrf.py", line 58, in wrapped_view 
    return view_func(*args, **kwargs) 
    File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/django/views/generic/base.py", line 68, in view 
    return self.dispatch(request, *args, **kwargs) 
    File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/djangorestframework-3.5.3-py2.7.egg/rest_framework/views.py", line 477, in dispatch 
    response = self.handle_exception(exc) 
    File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/djangorestframework-3.5.3-py2.7.egg/rest_framework/views.py", line 437, in handle_exception 
    self.raise_uncaught_exception(exc) 
    File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/djangorestframework-3.5.3-py2.7.egg/rest_framework/views.py", line 474, in dispatch 
    response = handler(request, *args, **kwargs) 
    File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/djangorestframework-3.5.3-py2.7.egg/rest_framework/generics.py", line 243, in post 
    return self.create(request, *args, **kwargs) 
    File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/djangorestframework-3.5.3-py2.7.egg/rest_framework/mixins.py", line 21, in create 
    self.perform_create(serializer) 
    File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/djangorestframework-3.5.3-py2.7.egg/rest_framework/mixins.py", line 26, in perform_create 
    serializer.save() 
    File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/djangorestframework-3.5.3-py2.7.egg/rest_framework/serializers.py", line 214, in save 
    self.instance = self.create(validated_data) 
    File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/djangorestframework-3.5.3-py2.7.egg/rest_framework/serializers.py", line 888, in create 
    raise_errors_on_nested_writes('create', self, validated_data) 
    File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/djangorestframework-3.5.3-py2.7.egg/rest_framework/serializers.py", line 780, in raise_errors_on_nested_writes 
    class_name=serializer.__class__.__name__ 
AssertionError: The `.create()` method does not support writable nested fields by default. 
Write an explicit `.create()` method for serializer `manager.serializers.EquipmentSerializer`, or set `read_only=True` on nested serializer fields. 

Ich bin nicht wirklich sicher, wie die richtige schreiben Erstellen und Aktualisieren von Funktionen, und ich verstehe nicht wirklich, wie es wird in der Dokumentation erklärt.

Code:

views.py:

from django.shortcuts import render 
from django.contrib.auth.models import User, Group 
from manager.serializers import * 
from rest_framework import generics 
from rest_framework import viewsets 
from rest_framework.decorators import api_view 
from rest_framework.response import Response 
from rest_framework.views import APIView 
from django.forms.models import model_to_dict 



class OrderSetDetails(generics.RetrieveUpdateDestroyAPIView): 
    queryset = Order.objects.all() 
    serializer_class = OrderSerializer 

class OrderSetList(generics.ListCreateAPIView): 
    queryset = Order.objects.all() 
    serializer_class = OrderSerializer 

class EquipmentSetDetails(generics.RetrieveUpdateDestroyAPIView): 
    queryset = Equipment.objects.all() 
    serializer_class = EquipmentSerializer 

class EquipmentSetList(generics.ListCreateAPIView): 
    queryset = Equipment.objects.all() 
    serializer_class = EquipmentSerializer 


class UserViewSet(viewsets.ModelViewSet): 

    queryset = User.objects.all().order_by('-date_joined') 
    serializer_class = UserSerializer 


class GroupViewSet(viewsets.ModelViewSet): 

    queryset = Group.objects.all() 
    serializer_class = GroupSerializer 

class ClientList(generics.ListCreateAPIView): 
    queryset = client.objects.all() 
    serializer_class = ClientSerializer 

serializers.py

from rest_framework import serializers 
from django.contrib.auth.models import User, Group 
from storage.models import * 


class AssignmentSerializer(serializers.HyperlinkedModelSerializer): 
    id = serializers.ReadOnlyField(source = 'Order.id') 
    name = serializers.ReadOnlyField(source = 'Order.name') 

    class Meta: 
     model = Assignment 
     fields = ('id', 'name', 'quantity') 


class EquipmentSerializer(serializers.ModelSerializer): 
    event = AssignmentSerializer(source= 'assignment_set', many = True) 
    class Meta: 
     model = Equipment 
     fields = '__all__' 


class ClientSerializer(serializers.ModelSerializer): 

    class Meta: 
     model = client 
     fields = '__all__' 

class UserSerializer(serializers.HyperlinkedModelSerializer): 
    class Meta: 
     model = User 
     fields = ('url', 'username', 'email', 'groups') 


class GroupSerializer(serializers.HyperlinkedModelSerializer): 
    class Meta: 
     model = Group 
     fields = ('url', 'name') 

class OrderSerializer(serializers.ModelSerializer): 
    class Meta: 
     model = Order 
     fields = '__all__' 

models.py:

from __future__ import unicode_literals 

from django.db import models 
from storage.choices import * 

# Create your models here. 
class Equipment(models.Model): 
    name = models.CharField(max_length=30) 
    fabricator = models.CharField(max_length=30, default='-') 
    storeplace = models.IntegerField() 
    labor = models.CharField(max_length=1, choices=labor_choices) 
    event = models.ManyToManyField('Order', blank = True, through= 'Assignment', through_fields=('Equipment', 'Order')) 
    max_quantity = models.IntegerField(default=1, null = True) 
    status = models.CharField(max_length=8, choices = STATUS_CHOICES, default = 'im Lager') 





    def __str__(self): 
     return self.name 




class client(models.Model): 
    firstname = models.CharField(max_length=30) 
    secondname = models.CharField(max_length=30) 
    email = models.EmailField() 
    post_code = models.IntegerField() 
    city = models.CharField(max_length=30) 
    street= models.CharField(max_length=30) 



    def __str__(self):    
     return "%s %s" % (self.firstname, self.secondname) 



class Order(models.Model): 
    name = models.CharField(max_length=30) 
    Type = models.CharField(
     max_length=2, 
     choices=TYPE_CHOICES, 
     default='Rental', 
     ) 
    city = models.CharField(max_length=30) 
    street= models.CharField(max_length=30) 
    date = models.DateField() 
    GuestNumber = models.IntegerField() 
    description = models.TextField() 
    client = models.ForeignKey("client", on_delete=models.CASCADE, blank = True, null = True) 
    status = models.CharField(max_length=30, choices=order_choices, default='glyphicon glyphicon-remove') 

    def __str__(self): 
     return self.name 

class Assignment(models.Model): 
    Equipment = models.ForeignKey('Equipment', on_delete=models.CASCADE) 
    Order = models.ForeignKey('Order', on_delete=models.CASCADE) 
    quantity = models.PositiveIntegerField(default=1) 

Vielen Dank im Voraus.

Answer 1

In Ihrem serializers.py ersetzen:

class EquipmentSerializer(serializers.ModelSerializer): 
    event = AssignmentSerializer(source= 'assignment_set', many = True) 
    class Meta: 
     model = Equipment 
     fields = '__all__' 

mit

class EquipmentSerializer(serializers.ModelSerializer): 
    # this is where the changes comes - read_only = True 
    event = AssignmentSerializer(source= 'assignment_set', many = True, read_only=True) 
    class Meta: 
     model = Equipment 
     fields = '__all__' 

Answer 2

DRF unterstützt keine create Methode für verschachtelte Serializer. Wenn Sie verknüpfte Felder in einem erweiterten Layout anzeigen möchten, nicht nur mit pks. Sie können die Methode to_representation überschreiben, anstatt das Standardfeld mtm neu zu schreiben. Und Sie shoulld eine create Methode überschreiben, da der dritte Modell in mtm Link:

class EquipmentSerializer(serializers.ModelSerializer): 

    class Meta: 
     model = Equipment 
     fields = '__all__' 

    def create(self, validated_data): 
     order = Order.objects.get(pk=validated_data.pop('event')) 
     instance = Equipment.objects.create(**validated_data) 
     Assignment.objects.create(Order=order, Equipment=Equipment) 
     return insance 

    def to_representation(self, instance): 
     representation = super(EquipmentSerializer, self).to_representation(instance) 
     representation['assigment'] = AssignmentSerializer(instance.assigment_set.all(), many=True).data 
     return representation 

Jetzt wird es mtm Felder richtig vorbei Liste von pks, wie [1, 2, 3] und zur Darstellung, dass mtm bezogene Modelle sparen, EquipmentSerializer wird verwenden AssignmentSerializer.