如何使用串行验证的基于函数的看法？ Django的休息

Question

我希望能够通过GET请求来更新实例。

URLs.朋友

urlpatterns=[
    url(
        r'^classes/(?P<pk>\d+)/add_student/(?P<student_id>\d+)', 
        views.add_student
    ),
]

views.朋友

def add_student(request, pk, student_id):
    class_ = get_object_or_404(Class, id=pk)
    student = get_object_or_404(Student, id=student_id)
    class_.students.add(student)
    return redirect('class-detail', pk=pk)

models.朋友

class Class(models.Model):
    students = models.ManyToManyField('Student', related_name='classes')
    ...

class Student(models.Model):
    ...

serialize人.朋友

class ClassSerializer(serializers.ModelSerializer):
    def validate(self, data):
        students = data['students']
        max_capacity = data['max_capacity']
        if len(students) > max_capacity:
            msg = 'This class is full'
            raise serializers.ValidationError(msg)

这将学生成功地添加到类，即使类是满的。如何更新这个样子，和学生被添加之前将其交由串行验证？

Answer 1

尝试这个：

def add_student(request, pk, student_id):
    class_ = get_object_or_404(Class, id=pk)

    # Change is here
    serializer = ClassSerializer(data=class_)
    serializer.is_valid(True)
    serialized_class_data = serializer.data

    student = get_object_or_404(Student, id=student_id)
    class_.students.add(student)
    return redirect('class-detail', pk=pk)

如果您需要通过串行验证，你需要通过数据/实例中使用的关键字参数data进行验证，并应调用.is_valid()方法。

欲了解更多信息，请参阅official DRF doc

UPDATE 根据您的更新和你views.py，您可以检查计数，而在validate()使用vserializer。

更改views.py如下：

from django.db.models import Count


def add_student(request, pk, student_id):
    class_ = get_object_or_404(Class, id=pk)
    std_count = class_.students.aggregate(count=Count('id'))['count']
    if std_count > max_capacity:
        return HttpResponse("This class is full")
    student = get_object_or_404(Student, id=student_id)
    class_.students.add(student)
    return redirect('class-detail', pk=pk)

Answer 2

http://www.django-rest-framework.org/api-guide/serializers/#validation

串行validate（）方法获得只有当你调用序列化对象is_valid（）方法调用。

改变你的方法是这样

def add_student(request, pk, student_id):
    class_ = get_object_or_404(Class, id=pk)
    serializer = ClassSerializer(data=class_)

    if serializer.is_valid():  # add student
        student = get_object_or_404(Student, id=student_id)
        class_.students.add(student)
        return redirect('class-detail', pk=pk)

    else:
        errors = serializer.errors
        # handle errors