[英]Django - User should only able to vote once
我希望用戶只能為類別請求投票一次,但不知何故我收到以下錯誤,我不知道此時如何“正確”調用實例:
無法分配“1”:“CategoryRequests_Voter.voted”必須是“CategoryRequests”實例。
模型.py
# Category Requests Model
class CategoryRequests(models.Model):
author = models.ForeignKey(User, on_delete=models.CASCADE)
....
# Vote(s) of Category Requests Model
class CategoryRequests_Voter(models.Model):
voter = models.ForeignKey(User, on_delete=models.CASCADE)
voted = models.ForeignKey(CategoryRequests, on_delete=models.CASCADE)
published_date = models.DateField(auto_now_add=True, null=True)
def publish(self):
self.published_date = timezone.now()
self.save()
視圖.py
def category_request_up_vote (request, pk):
category_request = get_object_or_404(CategoryRequests, pk=pk)
if request.method == 'GET':
if CategoryRequests_Voter.objects.filter(voter=request.user, voted=category_request.pk).exists():
messages.error(request, 'You already voted for this request.')
else:
category_request.up_vote = F('up_vote') + 1
category_request.save()
CategoryRequests_Voter.objects.create(voter=request.user, voted=category_request.pk)
messages.success(request, 'You have successfully Provided an Up-Vote for this Request')
return redirect('category_request_detail', pk=category_request.pk)
else:
messages.error(request, 'Uuups, something went wrong, please try again.')
return redirect('category_request_detail', pk=category_request.pk)
提前致謝
您需要將voted
參數修復為僅category_request
,而不是其主鍵,例如:
CategoryRequests_Voter.objects.create(voter=request.user, voted=category_request)
但是,您可以改進模型和視圖以提高一致性和優雅度。 為了防止User
投票兩次或更多次,您可以通過使用unique_together
約束來防止為同一個voter
創建兩次CategoryRequest_Voter
對象並voted
:
class CategoryRequests_Voter(models.Model):
voter = models.ForeignKey(User, on_delete=models.CASCADE)
voted = models.ForeignKey(CategoryRequests, on_delete=models.CASCADE)
published_date = models.DateField(auto_now_add=True, null=True)
class Meta:
unique_together = ('voter', 'voted')
def publish(self):
self.published_date = timezone.now()
self.save()
此外,我們可以使用get_or_create
從而只從數據庫中進行一次提取。 通常,更改數據的視圖應該使用 POST 請求而不是 GET 來執行此操作。 GET 請求不應該有副作用。
def category_request_up_vote (request, pk):
category_request = get_object_or_404(CategoryRequests, pk=pk)
if request.method == 'POST':
__, created = CategoryRequests_Voter.objects.get_or_create(
voter=request.user,
voted=category_request
)
if created:
category_request.up_vote = F('up_vote') + 1
category_request.save()
messages.success(request, 'You have successfully Provided an Up-Vote for this Request')
else:
messages.error(request, 'You already voted for this request.')
else:
messages.error(request, 'Uuups, something went wrong, please try again.')
return redirect('category_request_detail', pk=category_request.pk)
可能值得計算CategoryRequest_Voter
的數量,而不是增加投票計數,因為有可能,例如由於刪除User
或投票,最終投票數量不再與數量一致的CategoryRequests_Voter
■對於CategoryRequests
對象。
也許每次投票計算對象的數量並不是那么有效,但是您可以創建一個不時運行的任務,從而計算:
CategoryRequests_Voter.objects.filter(voted=category_request).count()
計算給定category_request
的CategoryRequests_Voter
的數量。
def category_request_up_vote (request, pk):
category_request = get_object_or_404(CategoryRequests, pk=pk)
try:
if request.method == 'GET':
if CategoryRequests_Voter.objects.filter(voter=request.user, voted=category_request).exists():
messages.error(request, 'You already voted for this request.')
return redirect('category_request_detail', pk=category_request.pk)
else:
category_request.up_vote = F('up_vote') + 1
category_request.save()
CategoryRequests_Voter.objects.create(voter=request.user, voted=category_request)
messages.success(request, 'You have successfully Provided an Up-Vote for this Request')
return redirect('category_request_detail', pk=category_request.pk)
else:
messages.error(request, 'Uuups, something went wrong, please try again.')
return redirect('category_request_detail', pk=category_request.pk)
except:
messages.error(request, 'Uuups, something went wrong, please try again.')
return redirect('category_request_detail', pk=category_request.pk)
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.