Question

我在数据库中有一个现有条目，我想检查我的views.py，如果该条目已存在于数据库中，如果确实如此，那么新值将替换该行中的旧数据，否则创建一个该用户的新行。我怎么能这样做？

#models.py
class Member(models.Model):
username = models.CharField(max_length=16, primary_key=True)
password = models.CharField(max_length=16)
profile = models.OneToOneField(Profile, null=True)
following = models.ManyToManyField("self", symmetrical=True)

class Message(models.Model):
user = models.ForeignKey(Member, related_name='%(class)s_user')
recip = models.ForeignKey(Member, related_name='%(class)s_recip')
pm = models.BooleanField(default=True)
time = models.DateTimeField()
text = models.CharField(max_length=4096)


def __str__(self):
    return self.username



#forms.py
class UploadFileForm(forms.ModelForm):
    class Meta:
        model = ProfilePic
        fields = ['text','thumbnail']

#models.py
class ProfilePic(models.Model):
    user = models.ForeignKey(Member, related_name='%(class)s_user', null=True)
    text = models.TextField(max_length=4096)
    thumbnail = models.FileField(upload_to='media', null=True)

#views.py
if request.POST:
username = request.session['username']
member_obj = Member.objects.get(pk=username)

    form = UploadFileForm(request.POST,request.FILES)
    profile_pic = form.save(commit=False) 

   **#checking if username already exists in the DB:**

    member_obj = Member.objects.update_or_create(username=username)

   **#if yes then replace data in the row with the new one,
     # if not create a new row**  

    profile_pic.user = member_obj
    profile_pic.save()

Answer 1

试试这个，

if request.method == 'POST':
    form = UploadFileForm(request.POST, request.FILES)
    if form.is_valid():
        cd = form.cleaned_data
        username = request.session['username']
        if Member.objects.filter(username=username).exists():
            member_obj = Member.objects.get(username=username)
            profile_pic = ProfilePic.objects.get(user=member_obj)
            profile_pic.user = member_obj
            # you can update other fields by using object.field_name (e.g. profile_pic.text = request.POST.get['text']
            profile_pic.save()
        else:
            ProfilePic.objects.create(user=username)
        return HttpResponse('success')
    else:
        return HttpResponse(form.errors)
else:
    form = UploadFileForm

Answer 2

您应该更改查询集：

member_obj = Member.objects.get(pk=username)

到

member_obj = Member.objects.get(username=username)

如果username = request.session['username']是username对象的user属性。如果您使用username s（而不是id），则必须强制执行不同的用户名。

如果您想使用pk（id），则应将其存储在会话中，然后查询将是：

user_id = request.session['id']
member_obj = Member.objects.get(pk=user_id)

Answer 3

正如你所做的那样，update_or_create就是为了这个。但是，您应该按如下方式使用它：

defaults = {} # Here you should specify the values that will be updated on the member object,
              # Or the default values to pass to the newly created instance

# Update or create return a tuple (object, created), created being a boolean
member_obj, created = Member.objects.update_or_create(username=username, defaults=defaults)

# This part seems correct to me
profile_pic.user = member_obj
profile_pic.save()

更新表单中数据库中的现有行 - Django

3 个答案: