Question

我正在尝试检查模型中是否已存在对象实例，或者它是否为空。我是Django的新手，我无法弄清楚在这里实现这一目标背后的逻辑。这是我的功能代码和我尝试做的事情（在views.py中）：

def registerAttendee(request,pk):
    act = Activity.objects.get(pk=pk)
    act.save()
    attendee, _ = Attendee.objects.get_or_create(student=request.user)
    if act.attendee.get(student=request.user) is None:
        act.attendee.add(attendee)
        messages.success(request, 'You\'re successfully registered as an attendee!', extra_tags='alert')
    else:
        messages.warning(request, 'You\'re already registered as an attendee!', extra_tags='alert')
        return redirect('home/#work')

我基本上检查，如果用户未在此活动中注册，那么我将添加他/她，但如果用户已经注册，我会显示特定的信息。我目前的代码不起作用，因为我得到了一个＆＃34;无效的语法＆＃34;单词无错误。我尝试用NULL和BLANK替换它，但我仍然遇到此错误。我该怎么替换它？

这就是我在models.py中所拥有的，如果有帮助的话：

class Attendee(models.Model):
student = models.ForeignKey(User, related_name="attendee")

class Activity(models.Model):
type = models.CharField(max_length=50, default="")
title = models.CharField(max_length=200, default="")
description = models.CharField(max_length=500)
owner = models.ForeignKey(User, related_name="owner")
college = models.CharField(max_length=200)
location = models.CharField(max_length=200)
room = models.CharField(max_length=200)
startDate = models.DateTimeField(null=True, blank=True)
endDate = models.DateTimeField(null=True, blank=True)
attendee = models.ManyToManyField(Attendee, related_name="attendees",null=True, blank=True)
volunteer = models.ManyToManyField(Volunteer, related_name="volunteers",null=True, blank=True)

Django if语句中的None和Null相当于什么

0 个答案: