在 Django 中查询以获取特定格式的数据答案

【问题标题】：Query to get data in particular format in Django在 Django 中查询以获取特定格式的数据
【发布时间】：2020-05-08 19:48:50
【问题描述】：

我的模特：

class Student(models.Model):
    name = models.CharField(max_length=100)
    email = models.CharField(max_length=100, unique=True)
    password = models.CharField(max_length=25)


class Subject(models.Model):
    name = models.CharField(max_length=100)


class Student_subject_mapping(models.Model):
    student = models.ForeignKey(Student, on_delete=models.CASCADE)
    subject = models.ForeignKey(Subject, on_delete=models.CASCADE)

我正在尝试以以下格式获取数据库中的所有Student_subject_mapping 数据：

以下列方式获取数据的查询是什么？如何实现上述格式的数据？

我的看法：

class Get_Students(APIView):

    def get(self, request):

        try:
            res = StudentSerializer(Student.objects.all(), many=True).data
            print({"results": res})
            return Response({"results": res}, status=status.HTTP_200_OK)

【问题讨论】：

标签： python django python-3.x django-rest-framework django-views

【解决方案1】：

models.py

class Student(models.Model):
    name = models.CharField(max_length=100)
    email = models.CharField(max_length=100, unique=True)
    password = models.CharField(max_length=25)

class Subject(models.Model):
    name = models.CharField(max_length=100)


class Student_subject_mapping(models.Model):
    student = models.ForeignKey(Student, on_delete=models.CASCADE, related_name='subjects')
    subject = models.ForeignKey(Subject, on_delete=models.CASCADE)

序列化器.py

class StudentSubjectMappingSerializer(serializers.ModelSerializer):
    id = serializers.SerializerMethodField()
    name = serializers.SerializerMethodField()

    def get_id(self, obj):
        return obj.subject.id

    def get_name(self, obj):
        return obj.subject.name

    class Meta:
        model = Student_subject_mapping
        fields = ['id', 'name']

class StudentSerializer(serializers.ModelSerializer):
    subjects = serializers.SerializerMethodField()

    def get_subjects(self, obj):
        return StudentSubjectMappingSerializer(obj.subjects.all(), many=True).data

    class Meta:
        model = Student
        fields = ['id', 'email', 'subjects']

您的查询

subjects = StudentSerializer(Student.objects.all(), many=True).data


print(json.dump({"results" : subjects}))

另外你不必为映射创建不同的表，你可以使用models.ManyToMantField例子

class Student(models.Model):
    name = models.CharField(max_length=100)
    email = models.CharField(max_length=100, unique=True)
    password = models.CharField(max_length=25)
    subjects = models.ManyToManyField(Subject)

class Subject(models.Model):
    name = models.CharField(max_length=100)

上述模型结构的序列化器

class SubjectSerializer(serializers.ModelSerializer):
    class Meta:
        model = Subject
        fields = ['id', 'name']

class StudentSerializer(serializers.ModelSerializer):
    subjects = serializers.SerializerMethodField()

    def get_subjects(self, obj):
        return SubjectSerializer(obj.subjects.all(), many=True).data

    class Meta:
        model = Student
        fields = ['id', 'email', 'subjects']

【讨论】：

嗨，Jeet，感谢您的回复，但我收到了“StudentSerializer(”的回复格式。@Jeet
@Zodiac 我的错。我忘了写.data 来获取序列化数据。我已经更新了我的答案，它现在应该可以工作了。立即尝试！
No @Jeet 我收到一个错误：尝试在序列化程序 SubjectSerializer 上获取字段 name 的值时出现 AttributeError。\n序列化程序字段可能命名不正确并且与任何属性不匹配或Student_subject_mapping 实例上的键。\n原始异常文本是：'Student_subject_mapping' 对象没有属性 'name'。"
你能发布你的views.py吗？
是的，发布！