無法通過WatchList實體訪問管理器如何解決此錯誤？

我正在嘗試通過 Django 創建一個電子商務網站（CS50 專案 2），并擁有一個具有多種形式的 Django 視圖。在這個視圖中，我試圖在 Django 表單中使用布爾欄位來使用戶能夠將串列添加到他的監視串列中，這兩個都是模型。在嘗試這樣做時，我收到了上述錯誤。

部分views.py

def listing(request, id):
    #gets listing
    listing = Listings.objects.get(id=id)
    watchlist_form = WatchListForm()
    if request.method == "POST":
        watchlist_form = WatchListForm(request.POST)
        if watchlist_form.is_valid():
            watchlist = watchlist_form.save(commit=False)
            watchlist.user = request.user
            watchlist.add_to_watchlist = True
            new_watchlist_listing = watchlist.objects.listings.add(listing) 
            return render(request, "auctions/listing.html",{
                "auction_listing": listing,
                "watchlistForm": watchlist_form
            })
        else:
            return render(request, "auctions/listing.html",{
                "auction_listing": listing,
                "form": comment_form,
                "comments": comment_obj,
                "bidForm": bid_form,
                "bids": bid_obj,
                "watchlistForm": watchlist_form
            })
    return render(request, "auctions/listing.html",{
        "auction_listing": listing,
        "form": comment_form,
        "comments": comment_obj,
        "bidForm": bid_form,
        "bids": bid_obj,
        "watchlistForm": watchlist_form
    })

模型.py

class Listings(models.Model):
    CATEGORY = [
    ("Miscellaneous", "Miscellaneous"),
    ("Movies and Television", "Movies and Television"),
    ("Sports", "Sports"),
    ("Arts and Crafts", "Arts and Crafts"),
    ("Clothing", "Clothing"),
    ("Books", "Books"),
]
    title = models.CharField(max_length=64)
    description = models.CharField(max_length=500)
    bid = models.DecimalField(max_digits=1000000000000, decimal_places=2)
    image = models.URLField(null=True, blank=True)
    category = models.CharField(max_length=64, choices=CATEGORY, default=None)
    user = models.ForeignKey(User, on_delete=models.CASCADE, default="")


class WatchList(models.Model):
    listings = models.ManyToManyField(Listings)
    user = models.ForeignKey(User, on_delete=models.CASCADE, default="")
    add_to_watchlist = models.BooleanField(default=False)

錯誤資訊

raise AttributeError("Manager isn't accessible via %s instances" % cls.__name__)
AttributeError: Manager isn't accessible via WatchList instances

由于這一行而發生此錯誤：new_watchlist_listing = watchlist.objects.listings.add(listing)。

uj5u.com熱心網友回復：

您添加帶有 的元素，因此沒有該部分。因此，您的視圖應如下所示：modelobject.manytomanyfield.add().objects

from django.contrib.auth.decorators import login_required
from django.shortcuts import get_object_or_404, redirect

@login_required
def listing(request, id):
    listing = get_object_or_404(Listings.objects, pk=id)
    watchlist_form = WatchListForm()
    if request.method == "POST":
        watchlist_form = WatchListForm(request.POST)
        if watchlist_form.is_valid():
            watchlist_form.instance.user = request.user
            watchlist_form.instance.add_to_watchlist = True
            watchlist = watchlist_form.save()
            watchlist.listings.add(listing)
            return redirect('name-of-the-view')
    return render(request, 'auctions/listing.html',{
        'auction_listing': listing,
        'form': comment_form,
        'comments': comment_obj,
        'bidForm': bid_form,
        'bids': bid_obj,
        'watchlistForm': watchlist_form
    })

注意：通常最好使用^[Django-doc]，然后直接使用^[Django-doc]。如果物件不存在，例如因為用戶自己更改了 URL，將導致回傳HTTP 404 Not Found回應，而 using 將導致HTTP 500 Server Error。get_object_or_404(…) .get(…) get_object_or_404(…).get(…)

注意：如果 POST 請求成功，您應該制作一個^[Django-doc] 來實作Post/Redirect/Get模式 ^[wiki]。這樣可以避免在用戶重繪 瀏覽器時發出相同的 POST 請求。redirect

注意：您可以使用@login_required裝飾器 ^[Django-doc]將視圖限制為經過身份驗證的用戶的視圖 。

注意：通常最好不要在使用方法 ^[Django-doc]commit=False保存表單時使用：這將避免保存多對多關系，因為只有在提交專案時才能保存這些關系。通常最好更改表單中的包裹。有關更多資訊，請參閱我的文章^{[Django-antipatterns]}。.save(…).instance

標籤：Python django cs50

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