DJANGO：如何编写自定义序列化器，以从相关模型中添加字段？

Question

型号：

class Subject(models.Model):
    db = 'default'
    subjectName = models.CharField(max_length = 100)
    cohortID = models.ForeignKey(Cohort, on_delete=models.CASCADE, related_name='subjects')
    teacherID = models.ForeignKey(Teacher, on_delete=models.CASCADE, related_name='subjects', null=True)

class Cohort(models.Model):
    db = 'default'
    school_creator = models.ForeignKey(CustomUser, on_delete = models.CASCADE, related_name='cohorts')
    mainTeacherID = models.ForeignKey(CustomUser, on_delete=models.CASCADE, null=True, related_name='mainCohorts')
    class_name = models.CharField(max_length = 100)

序列化器：

class SubjectSerializer(serializers.ModelSerializer):
    class Meta:
        model = models.Subject
        fields = ('subjectName', 'teacherID', 'pk',)

这是上面使用序列化程序的响应：

{"subjectName":"Maths","teacherID":2,"pk":4}

我想拥有：

{"subjectName":"Maths","teacherID":2,"pk":4, "cohortName" : "4 B"}

cohortName应该来自模型Cohort.class_name。我猜是有可能这样做的，因为Subject是通过ForeignKey Subject.cohortID连接到同类群组的。我尝试添加一些自定义序列化程序：

class SubjectCohortSerializer(serializers.ModelSerializer):
    cohortName = serializers.SerializerMethodField(read_only=True)
    class Meta:
        model = models.Subject
        fields = ('subjectName', 'teacherID', 'pk','cohortName')
    def get_cohortName(self, subject):
        return models.Cohort.objects.get(pk=self.context['request'].cohortID.className)

但是肯定我做错了，而且很难掌握上面的序列化程序中发生的事情。

Answer 1

将您的get_cohortName()方法更改为，

class SubjectCohortSerializer(serializers.ModelSerializer):
    cohortName = serializers.SerializerMethodField(read_only=True)

    class Meta:
        model = models.Subject
        fields = ('subjectName', 'teacherID', 'pk', 'cohortName')

    def get_cohortName(self, subject):
        return subject.cohortID.className