由于外键约束失败而导致创建Django对象失败(IntegrityError )

Question

我的网站有一个评论部分，用户可以在产品上留下评论。产品页面上的注释将存储在一个名为“ProductReview”的模型中。下面是模型的代码：

    class ProductReview(models.Model):
        product = models.ForeignKey(Product, related_name='reviews', on_delete=models.CASCADE)
        name = models.CharField(blank=True,max_length=20)
        stars = models.IntegerField()
        content = models.TextField(blank=True)
        date_added = models.DateTimeField(auto_now_add=True)
        created_by = models.OneToOneField(User, on_delete=models.CASCADE)

现在，与模型关联的视图如下所示--注意:整个视图与错误无关。与保存注释相关的部分是第二个'request.POST‘，我使用#表示了这个注释：

def product(request, category_slug, product_slug):
    cart = Cart(request)
    product = get_object_or_404(Product, category__slug=category_slug, slug=product_slug)

    if request.method == 'POST':
        form = AddToCartForm(request.POST)

        if form.is_valid():
            quantity = form.cleaned_data['quantity']
            cart.add(product_id=product.id, quantity=quantity, update_quantity=False)
            messages.success(request, 'The product was added to the cart')
            return redirect('product', category_slug=category_slug, product_slug=product_slug)

    similar_products = list(product.category.products.exclude(id=product.id))

    # this part is for saving of the user comments to productreview model
    if request.method == 'POST':
        stars = request.POST.get('stars', 3)
        content = request.POST.get('content', '')
        name = request.POST.get('name', '')
        created_by = request.user

        review = ProductReview.objects.create(product=product, name=name, stars=stars, content=content, created_by=created_by)
        return HttpResponseRedirect(request.META.get('HTTP_REFERER'))
    # this marks the end of the code relevant to saving the user comment 

    if len(similar_products) >= 4:
        similar_products = random.sample(similar_products, 4)

    user_type = 0
    if request.user.is_authenticated:
        user_type = UserType.objects.filter(created_by=request.user.id).values_list('user_type', flat=True)
        user_type = int(user_type[0])
    return render(request, 'product.html', {'product': product, 'similar_products': similar_products, 'user_type': user_type})

最后，在视图中引用的模板'product.html‘的相关部分

{% if request.user.is_authenticated %}
        {% if user_type == 2 %}
            <div class="notification space-below">
                <form method="post" action=".">
                    {% csrf_token %}


                     <div class="field">
                        <label>Name</label>
                        <div class="control">
                            <input class="text" name="name" value="{{ request.user }}" readonly>
                        </div>
                    </div>


                    <div class="field">
                        <label>Stars</label>
                        <div class="control">
                             <div class="select">
                                 <select name="stars">
                                     <option value="1">1</option>
                                     <option value="2">2</option>
                                     <option value="3" selected>3</option>
                                     <option value="4">4</option>
                                     <option value="5">5</option>

                                 </select>
                             </div>
                        </div>
                    </div>

                    <div class="field">
                        <label>Content</label>
                        <div class="control">
                            <textarea class="textarea" name="content"></textarea>
                        </div>
                    </div>

                    <div class="field">
                        <div class="control">
                            <button class="button is-success">Submit</button>
                        </div>
                    </div>

                </form>
            </div>

            {% else %}
                <div>sign in with a buyer account to leave review</div>

            {% endif %}
    {% endif %}

现在，当我试图在product.html页面中填写表单并提交它时，我会得到以下错误：

FOREIGN KEY constraint failed
IntegrityError at /smartwatch/apple-watch/

有人能说出我的代码到底有什么问题吗？

Answer 1

非常肯定，所有这些都适用于您的模型，特别是这一行：

    created_by = models.OneToOneField(User, on_delete=models.CASCADE)

您正在使用OneToOneField。这意味着单个用户将能够在整个应用程序中留下一个检查。您正在获得完整性错误，可能是因为您选择的这个用户已经对不同的产品进行了审查。

如果这不是您想要的，那么使用普通的ForeignKey代替。

我认为您的目的是确保单个用户只能在每个产品上留下一个评论。在这种情况下，您应该尝试在product和created_by字段之间设置created_by。