如何解决Django应用程序中的错误“'NoneType'对象没有属性'day'”

Question

我在我的应用程序中注意到了这个错误，“'NoneType' 对象没有属性 'day'”。我注意到的是。我有一个名为 course_schedule 的模型，课程表有周一到周日的选项。如果课程表是部分填充的，也就是说我只填充了几天，比如一周中完整的 7 天中的 3 天，我会收到错误消息，但是每当我填充课程表时，我会完全填充课程表模型，我不会有错误，一切正常。

错误日志：

Traceback (most recent call last):
  File "C:\Users\Habib\Documents\django\FIVERR\Ayyub_SMS\venv\lib\site-packages\django\core\handlers\exception.py", line 47, in inner
    response = get_response(request)
  File "C:\Users\Habib\Documents\django\FIVERR\Ayyub_SMS\venv\lib\site-packages\django\core\handlers\base.py", line 181, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "C:\Users\Habib\Documents\django\FIVERR\Ayyub_SMS\sms\schoolapp\views.py", line 1754, in sir_course
    get_all = getall(2021, sch.day)

Exception Type: AttributeError at /en/sir_course
Exception Value: 'NoneType' object has no attribute 'day'

models.py

class Assign_teacher_to_courses(models.Model):
    Course_Name = models.ForeignKey(add_courses, on_delete=models.CASCADE)
    Teacher_Name = models.ForeignKey(add_teacher_by_manager, on_delete=models.CASCADE)

    def __str__(self):
        return self.Course_Name.Course_Name+" - "+self.Teacher_Name.teacher_ID+" - "+self.Teacher_Name.teacher_name

class course_schedule(models.Model):

    days_choices = (
        ("Mon", 'Monday'),
        ("Tue", 'Tuesday'),
        ('Wed', "Wednessday"),
        ('Thurs', "Thursday"),
        ('Fri', "Friday"),
        ('Sat', "Saturday"),
        ("Sun", "Sunday"),
    )

    day = models.CharField(max_length=60, default="Sun")
    time_session = models.CharField(max_length=150, default='8:00am')
    end_session = models.CharField(max_length=150, default='10:00am')

    def __str__(self):
        return self.day

views.py

def sir_course(request):
    if request.method == "POST":
        get_course_name_th = Assign_teacher_to_courses.objects.filter(Teacher_Name=get_id_teach)
        # print(get_course_name_th)

        store_email_teacher_dtta = store_email_teach_new.objects.filter(Teacher_ID=teach_course_id)

        days = {}

        for course in get_course_name_th:

            # print(course.Course_Name.syllabus)

            sch = course_schedule.objects.get(id=course.Course_Name.pk)

            get_all = getall(2021, sch.day)

            lists = {}
            for n in get_all:

                date = n.strftime("%d/%m/%Y")

                try:
                    if days[str(date)]:

                        days[str(date)].append(str(course.Course_Name.Course_Name)+" "+str(course.Course_Name.course_code))

                except KeyError:

                    days[str(date)] = [str(course.Course_Name.Course_Name)+" "+str(course.Course_Name.course_code),]

        # print(days)

        context1 = {'get_course_name_t_cours':get_course_name_th, "days": days}

        return render(request, 'teacher_page.html', context1)

    else:
        return redirect('/')

Answer 1

看起来 sch 可能是 None。

您应该始终将您的对象放在 try...except 块中，或者您可以使用内置的get_object_or_404

Answer 2

跟随您的add_courses 模型的previous question sn-p。

class add_courses(models.Model):
    Course_Name = models.CharField(max_length=200, blank=True)
    Manager_Name = models.ForeignKey(Manager_login_information, on_delete=models.CASCADE, blank=True)
    description = models.TextField(default='', blank=True)
    syllabus = models.TextField(default='', blank=True)
    student = models.ManyToManyField(add_students_by_manager, blank=True)
    schedule = models.ForeignKey(course_schedule, on_delete=models.CASCADE, blank=True)

    def __str__(self):
        return self.Course_Name

您有以下从Assign_teacher_to_courses 到course_schedule 的关系路径：

Assign_teacher_to_courses -> add_courses -> course_schedule

因此，要获取get_course_name_th 中每个course 的时间表，您应该将sch = course_schedule.objects.get(id=course.Course_Name.pk) 更改为sch = course.Course_Name.schedule。