django 抓取表单输入并编辑实例

Question

我正在尝试制作一个简单的库存应用程序，但我在补货逻辑方面遇到了问题，例如，如果我购买了一只新股票，价格与我想要的第一只股票不同，只需在壳牌中获取整个股票的平均价格就可以正常工作，但是当我转到我的表单时，我总是得到表单输入而不是所需的值， 经过一番调查，我发现我正在使用请求获取实例数据。POST.get 甚至在保存数量 = 项目数量之前！！我现在的问题是我如何分别获取我的输入和实例

##models 
class Supply(models.Model):
    name = models.CharField(max_length=100, unique=True)
    quantity = models.PositiveIntegerField()
    price = models.DecimalField(max_digits=11, decimal_places=2)
    created = models.DateField(auto_now_add=True)
    last_modefied = models.DateField(auto_now=True)
    def __str__(self):
        return self.name
##form
class SupplyForm(forms.ModelForm):
    class Meta:
        model = Supply
        fields = ["name", "quantity", "price"]
#view
def add_supply(request):
    form = SupplyForm()
    if request.POST:
        # getting form input data
        name = request.POST.get("name")
        quantity = request.POST.get("quantity")
        price = request.POST.get("price")
        # getting Supply instance
        item = Supply.objects.get(name=name)
        # instantiating the form
        form = SupplyForm(request.POST, instance=item)
        if form.is_valid:
                # Logic
            old_supply = item.quantity * item.price
            new_supply = int(quantity) * int(price)
            new_quantity = item.quantity + int(quantity)
            item.price = (old_supply + new_supply) / new_quantity
            item.quantity = new_quantity
            form.save()
            return redirect("project_list")
    return render(request, "restock.html", {"form": form}) 

Answer 1

找到了这个答案，谁可能需要它：首先删除模型表单并制作表单。具有 2 个新字段的表单类似

#forms
      class RestockForm(forms.Form):
            name = forms.CharField(max_length="30")
            quantity = forms.IntegerField(min_value=0)
            price = forms.DecimalField(max_digits=11, decimal_places=2)
            new_quantity = forms.IntegerField(min_value=0)
            new_price = forms.DecimalField(max_digits=11, decimal_places=2)
#views
    def add_supply(request, pk):
        #getting the object
        item = get_object_or_404(Supply, pk=pk)
        # instantiating the form on using initial since its not a model form
        form = RestockForm(initial={"name": item.name, "quantity": item.quantity, "price": item.price})
        if request.POST:
            # getting form extra input data
            quantity = request.POST.get("new_quantity")
            price = request.POST.get("new_price")
            form = RestockForm(request.POST,)
            if form.is_valid():
                old_supply = item.quantity * item.price
                new_supply = int(quantity) * int(price)
                _quantity = item.quantity + int(quantity)
                item.price = (old_supply + new_supply) / _quantity
                item.quantity = _quantity
                # important need to save the object
                item.save()
                return redirect("project_list")
        return render(request, "restock.html", {"form": form})
#urls
path('restock/<int:pk>', stock_views.add_supply, name="restock"),