在保存表单之前验证数据库值

Question

(首先对不起，标题含糊不清 - 我不知道如何描述这个标题中的问题(

我有两个模型，如下所示。

PRODUCT_TYPE=(('TL','Tubeless Tyre'), ('TT','Tubed Tyre'), ('NA','Not applicable'))
FRONT_BACK=(('F','Front'), ('B','Back'), ('C','Common'))
class Product(models.Model):
    product_group=models.ForeignKey('productgroup.ProductGroup', null=False,blank=False)
    manufacturer=models.ForeignKey(Manufacturer, null=False,blank=False)
    product_type=models.CharField(max_length=2, choices=PRODUCT_TYPE,)
    opening_stock=models.PositiveIntegerField(default=0)
    def __str__(self):
        return '%s (%s, %s, %s) balance = %d ' % (self.product_group, self.manufacturer, self.product_type ,self.get_balance_stock())
    class Meta:
        unique_together = ('product_group', 'manufacturer','product_type')
    def get_total_stock_in(self):
        return Stock.objects.filter(product=self.id,ttype='I').aggregate(Sum('quantity'))
    def get_total_stock_out(self):
        return Stock.objects.filter(product=self.id,ttype='O').aggregate(Sum('quantity'))
    def get_balance_stock(self):
        return (self.opening_stock+self.get_total_stock_in()['quantity__sum']
                - self.get_total_stock_out()['quantity__sum'])
TRANSACTION_TYPE=(('I','Stock In'),('O','Stock Out'))
class Stock(models.Model):
    product=models.ForeignKey('product.Product', blank=False,null=False)
    date=models.DateField(blank=False, null=False,)
    quantity=models.PositiveIntegerField(blank=False, null=False)
    ttype=models.CharField(max_length=1,verbose_name="Ttransaction type",choices=TRANSACTION_TYPE, blank=False)
    added_date=models.DateTimeField(blank=False, auto_now=True)

我制作了一个模型表格和两个单独的视图来记录进货和缺货，如下所示。

class StockInOutForm(forms.ModelForm):
    class Meta:
        model = Stock
        fields=['product','quantity','date'] #'ttype',
        widgets = {
            'date': forms.DateInput(attrs={'class': 'datepicker'}),
        } 
class StockIn(CreateView):
    model=Stock
    form_class=StockInOutForm
    def get_context_data(self, **kwargs):
        context = super(StockIn, self).get_context_data(**kwargs)
        context['ttype']="Stock In"
        return context
    def form_valid(self, form):
        stockin = form.save(commit=False)
        stockin.ttype = 'I'
        stockin.save()
        return http.HttpResponseRedirect(reverse('stock_list'))
class StockOut(CreateView):
    model=Stock
    form_class=StockInOutForm   
    def get_context_data(self, **kwargs):
        context = super(StockOut, self).get_context_data(**kwargs)
        context['ttype']="Stock Out"
        return context
    def form_valid(self, form):
        stockout = form.save(commit=False)
        stockout.ttype = 'O'
        stockout.save()
        return http.HttpResponseRedirect(reverse('stock_list'))

现在，如何防止数量大于可用库存的缺货操作？

我相信我可以从相应的产品对象调用该方法get_balance_stock()，并将值与表单中给出的当前quantity进行比较。

请给出一些有关如何实现它的说明。

谢谢。

Answer 1

您应该在窗体类上定义一个clean方法。您可能希望对缺货操作使用单独的子类，因为此验证应仅适用于这些操作。

class StockOutForm(StockInOutForm):
    def clean(self):
        product = self.cleaned_data['product']
        available = product.get_balance_stock()
        if self.cleaned_data['quantity'] > available:
            raise forms.ValidationError("You can't take out more stock of {} than is available ({})".format(product, available)