python - 如何在 django Rest 框架中使用外键进行计数

Question

这是我的 models.py

class Language(models.Model):
    language_id     = models.BigAutoField(primary_key=True)
    language_name   = models.CharField(max_length=255)
    created_on      = models.DateTimeField(auto_now=True)
    latest_build_on = models.DateTimeField(auto_now_add=True)
    latest_version  = models.DecimalField(max_digits=5, decimal_places=2)
    company         = models.OneToOneField('Company',on_delete=models.CASCADE,related_name='language')

    def __str__(self):
        return self.language_name

class Frameworks(models.Model):
    framework_id    = models.BigAutoField(primary_key=True)
    framework_name  = models.CharField(max_length=255)
    framework_logo  = models.FileField()
    created_on      = models.DateTimeField(auto_now=True)
    latest_build_on = models.DateTimeField(auto_now_add=True)
    latest_version  = models.DecimalField(max_digits=5, decimal_places=2)
    language        = models.ForeignKey('Language',on_delete=models.CASCADE,related_name='frameworks')

    def __str__(self):
        return self.framework_name

class Technologies(models.Model):
    technology_id   = models.BigAutoField(primary_key=True)
    technology_name = models.CharField(max_length=255)
    description     = models.TextField()
    language        = models.ManyToManyField('Language',related_name='technology')

    def __str__(self):
         return self.technology_name

这里是serializers.py

class GetLanguageSerializer(serializers.ModelSerializer):
    technology = serializers.StringRelatedField(many=True)
    frameworks = serializers.StringRelatedField(many=True)
    class Meta:
        model = Language
        fields = ('language_name','created_on','latest_build_on','latest_version','company','technology','frameworks')
        depth = 1

class LanguageSerializer(serializers.ModelSerializer):
    class Meta:
        model = Language
        fields = ('language_name','created_on','latest_build_on','latest_version','company')

class GetFrameworksSerializer(serializers.ModelSerializer):
    language = serializers.StringRelatedField()
    class Meta:
        model = Frameworks
        fields = '__all__'
        depth = 1

class FrameworksSerializer(serializers.ModelSerializer):
    class Meta:
        model = Frameworks
        fields = '__all__'

这是我的观点.py

class LanguageView(viewsets.ModelViewSet):
    queryset =  Language.objects.all()
    serializer_class = LanguageSerializer
    filter_backends = [SearchFilter,OrderingFilter]
    search_fields = ['language_name']

    def get_serializer_class(self):
        serializer_class = self.serializer_class
        if self.request.method == 'GET':
            serializer_class = GetLanguageSerializer
        return serializer_class

class FrameworksView(viewsets.ModelViewSet):
    queryset =  Frameworks.objects.all()
    serializer_class = FrameworksSerializer
    filter_backends = [SearchFilter,OrderingFilter]
    search_fields = ['framework_name']


    def get_serializer_class(self):
        serializer_class = self.serializer_class
        if self.request.method == 'GET':
            serializer_class = GetFrameworksSerializer
        return serializer_class

这里我得到这样的API:

[
  {
    "language_name": "python",
    "created_on": "2018-10-03T04:59:37.407717Z",
    "latest_build_on": "2018-10-03T04:59:37.407801Z",
    "latest_version": "3.60",
    "company": {
      "company_id": 1,
      "company_name": "Guido van dom rossum",
      "started_from": "2018-10-03T04:58:54.889132Z",
      "country": "Netherland",
      "email": "<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="1a727f766a5a6a636e72757434797577" rel="noreferrer noopener nofollow">[email protected]</a>",
      "website": "https://python.org",
      "ip": "127.0.0.1",
      "active": true
    },
    "technology": [
      "blockchain",
      "machine learning"
    ],
    "frameworks": [
      "django",
      "flask",
      "bottle"
    ]
  }
]

但我期待:

[
  {
    "language_name": "python",
    "created_on": "2018-10-03T04:59:37.407717Z",
    "latest_build_on": "2018-10-03T04:59:37.407801Z",
    "latest_version": "3.60",
    "total_technology":2,
    "toatl_frameworks": 3,
    "company": {
      "company_id": 1,
      "company_name": "Guido van dom rossum",
      "started_from": "2018-10-03T04:58:54.889132Z",
      "country": "Netherland",
      "email": "<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="69010c05192919101d010607470a0604" rel="noreferrer noopener nofollow">[email protected]</a>",
      "website": "https://python.org",
      "ip": "127.0.0.1",
      "active": true
    },
    "technology": [
      "blockchain",
      "machine learning"
    ],
    "frameworks": [
      "django",
      "flask",
      "bottle"
    ]
  }
]

在我的 api 中我期待

"total_technology":2,
"toatl_frameworks": 3,

这两个额外的字段按组计数“技术”和“框架”请看看我的代码..

如果是相同型号则不是问题。但在这里我想要外键所以我很困惑..

Answer 1

使用SerializerMethodField()在你的序列化器中

class GetLanguageSerializer(serializers.ModelSerializer):
    technology = serializers.StringRelatedField(many=True)
    frameworks = serializers.StringRelatedField(many=True)

    <b>total_technology = serializers.SerializerMethodField(read_only=True)
    toatl_frameworks = serializers.SerializerMethodField(read_only=True)

    def get_toatl_frameworks(self, language):
        return language.frameworks.count()

    def get_total_technology(self, language):
        return language.technology.count() # change 'technology' with corresponding "related_name" value</b>

    class Meta:
        model = Language
        <b>fields = (other_fileds, 'total_technology', 'toatl_frameworks')</b>
        depth = 1