파이썬 장고 프레임워크를 사용해서 API 서버 만들기 (5)

RelatedField

polls_api/serializers.py

class ChoiceSerializer(serializers.ModelSerializer): 
    class Meta:
        model = Choice
        fields = ['choice_text', 'votes']

class QuestionSerializer(serializers.ModelSerializer):
    owner = serializers.ReadOnlyField(source='owner.username')
    choices = ChoiceSerializer(many=True, read_only=True)
    
    class Meta:
        model = Question
        fields = ['id', 'question_text', 'pub_date', 'owner', 'choices']

class UserSerializer(serializers.ModelSerializer):
    #questions = serializers.PrimaryKeyRelatedField(many=True, queryset=Question.objects.all())
    #questions = serializers.StringRelatedField(many=True, read_only=True)
    #questions = serializers.SlugRelatedField(many=True, read_only=True, slug_field='pub_date')
    questions = serializers.HyperlinkedRelatedField(many=True, read_only=True, view_name='question-detail')
    
    class Meta:
        model = User
        fields = ['id', 'username', 'questions']

polls_api/urls.py

from django.urls import path,include
from .views import *

urlpatterns = [
    path('question/', QuestionList.as_view(), name='question-list'),
    path('question/<int:pk>/', QuestionDetail.as_view(),name='question-detail'),
    path('users/', UserList.as_view(),name='user-list'),
    path('users/<int:pk>/', UserDetail.as_view()),
    path('register/', RegisterUser.as_view()),
    path('api-auth/', include('rest_framework.urls'))
]

polls/models.py

...
class Choice(models.Model):
    question = models.ForeignKey(Question, related_name='choices', on_delete=models.CASCADE)
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)

    def __str__(self):
        return self.choice_text

투표(Votes) 기능 구현하기 - Models

polls/models.py

from django.contrib.auth.models import User

class Vote(models.Model):
    question = models.ForeignKey(Question, on_delete=models.CASCADE)
    choice = models.ForeignKey(Choice, on_delete=models.CASCADE)
    voter = models.ForeignKey(User, on_delete=models.CASCADE)
    
    class Meta:
        constraints = [
            models.UniqueConstraint(fields=['question', 'voter'], name='unique_voter_for_questions')
        ]

polls_api/serializers.py

class ChoiceSerializer(serializers.ModelSerializer):
    votes_count = serializers.SerializerMethodField()
    
    class Meta:
        model = Choice
        fields = ['choice_text', 'votes_count']
        
    def get_votes_count(self, obj):
        return obj.vote_set.count()

Django Shell

...
>>> from polls.models import *
>>> question = Question.objects.first()
>>> choice = question.choices.first()
>>> from django.contrib.auth.models import User
>>> user= User.objects.get(username='luke')
>>> Vote.objects.create(voter=user,question=question,choice=choice)
<Vote: Vote object (1)>
>>> question.id
1

투표(Votes) 기능 구현하기 - Serializers & Views

polls_api/serializers.py

from polls.models import Question,Choice, Vote

class VoteSerializer(serializers.ModelSerializer):    
    voter = serializers.ReadOnlyField(source='voter.username')
        
    class Meta:
        model = Vote
        fields = ['id', 'question', 'choice', 'voter']

polls_api/views.py

from polls.models import Question,Choice, Vote
from polls_api.serializers import VoteSerializer
from .permissions import IsOwnerOrReadOnly , IsVoter

class VoteList(generics.ListCreateAPIView):
    serializer_class = VoteSerializer
    permission_classes = [permissions.IsAuthenticated]
    
    def get_queryset(self, *args, **kwargs):
        return Vote.objects.filter(voter=self.request.user)
   
    def perform_create(self, serializer):
        serializer.save(voter=self.request.user)
  
class VoteDetail(generics.RetrieveUpdateDestroyAPIView):
    queryset = Vote.objects.all()
    serializer_class = VoteSerializer
    permission_classes = [permissions.IsAuthenticatedOrReadOnly, IsVoter]

polls_api/permissions.py

class IsVoterOrReadOnly(permissions.BasePermission):
    def has_object_permission(self, request, view, obj):
        return obj.voter == request.user

polls_api/urls.py

from django.urls import path, include
from .views import VoteList, VoteDetail

urlpatterns = [
    ...
    path('vote/', VoteList.as_view()),
    path('vote/<int:pk>/', VoteDetail.as_view()),
]

Validation

polls_api/serializers.py

from rest_framework.validators import UniqueTogetherValidator

class VoteSerializer(serializers.ModelSerializer):
    def validate(self, attrs):
        if attrs['choice'].question.id != attrs['question'].id:
            raise serializers.ValidationError("Question과 Choice가 조합이 맞지 않습니다.")
        
        return attrs
    
    class Meta:
        model = Vote
        fields = ['id', 'question', 'choice', 'voter']
        validators = [
            UniqueTogetherValidator(
                queryset=Vote.objects.all(),
                fields=['question', 'voter']
            )
        ]

polls_api/views.py

from rest_framework import status
from rest_framework.response import Response

class VoteList(generics.ListCreateAPIView):
    serializer_class = VoteSerializer
    permission_classes = [permissions.IsAuthenticated]
    
    def get_queryset(self, *args, **kwargs):
        return Vote.objects.filter(voter=self.request.user)
    
    def create(self, request, *args, **kwargs):
        new_data = request.data.copy()
        new_data['voter'] = request.user.id
        serializer = self.get_serializer(data=new_data)
        serializer.is_valid(raise_exception=True)
        self.perform_create(serializer)
        headers = self.get_success_headers(serializer.data)
        return Response(serializer.data, status=status.HTTP_201_CREATED, headers=headers)
    
class VoteDetail(generics.RetrieveUpdateDestroyAPIView):
    queryset = Vote.objects.all()
    serializer_class = VoteSerializer
    permission_classes = [permissions.IsAuthenticated, IsVoter]
    
    def perform_update(self, serializer):
        serializer.save(voter=self.request.user)

Testing

자동화된 테스트

polls_api/test.py

from django.test import TestCase
from polls_api.serializers import QuestionSerializer

class QuestionSerializerTestCase(TestCase):
    def test_with_valid_data(self):
        serializer = QuestionSerializer(data={'question_text': 'abc'})
        self.assertEqual(serializer.is_valid(), True)
        new_question = serializer.save()
        self.assertIsNotNone(new_question.id)
        
    def test_with_invalid_data(self):
        serializer = QuestionSerializer(data={'question_text': ''})
        self.assertEqual(serializer.is_valid(), False)

테스트 실행하기

python manage.py test

Testing Serializers

polls_api/tests.py

class VoteSerializerTest(TestCase):
    def setUp(self):
        self.user = User.objects.create(username='testuser')
        self.question = Question.objects.create(
            question_text='abc',
            owner=self.user,
        )
        self.choice = Choice.objects.create(
            question=self.question
            choice_text='1'
        )    
    
   def test_vote_serializer(self):  
        self.assertEqual(User.objects.all().count(), 1)
        data = {
            'question': self.question.id
            'choice': self.choice.id
            'voter': self.user.id
        }
        serializer = VoteSerializer(data=data)
        self.assertTrue(serializer.is_valid())
        vote = serializer.save()
    
        self.assertEqual(vote.question, self.question)
        self.assertEqual(vote.choice, self.choice)
        self.assertEqual(vote.voter, self.user)
    
    def test_vote_serializer_with_duplicate_vote(self):
        self.assertEqual(User.objects.all().count, 1)
        choice1 = Choice.objects.create(
            quetsion=self.question,
            choice_text='2'
        )
        Vote.objects.create(question=self.question, choice=self.choice, voter=self.user)
    
        data = {
            'question': self.question.id
            'choice': self.choice.id
            'voter': self.user.id
        }
        serializer = VoteSerializer(data=data)
        self.assertTrue(serializer.is_valid())
    
    def test_vote_serilaizer_with_unmatched_question_and_choice(self):
        question2 = Question.objects.create(
            question_text='abc',
            owner=self.user,
        )
    
        choice2 = Choice.objects.create(
            quetsion=question2,
            choice_text='1'
        )
        data = {
            'question': self.question.id
            'choice': self.choice.id
            'voter': self.user.id
        }
        serializer = VoteSerializer(data=data)
        self.assertTrue(serializer.is_valid())