Question

我想将金额作为整数存储在数据库中。为方便起见，我还添加了浮点字段：

# File: models.py 
class Transaction(models.Model):
    user = models.ForeignKey(User, related_name='transactions')
    date = models.DateTimeField(default=datetime.now)
    # transacted btc-amount in satoshi; positive when I bought btc, negative else
    amount_btc_satoshi = models.IntegerField()
    # for convenience: transacted btc-amout in units of 1 btc
    amount_btc = models.FloatField(null=True)
    # transacted fiat-amount in 1e-5 euros; positive when I sold btc, negative else
    amount_eur_milicent = models.IntegerField()
    # for convenience: transacted fiat-amout in units of 1 eur
    amount_eur = models.FloatField(null=True)
    # True if I bought bitcoins, False if I sold bitcoins
    is_bid = models.BooleanField()
    # effective fiat price per 1 BTC in EUR
    price_per_btc = models.FloatField()

为方便起见，我覆盖了ModelForm派生中的save方法。它应该根据amount_btc和amount_eur自动更新某些相关字段：

# File: forms.py
class TransactionForm(forms.ModelForm):
    def clean(self):
        cleaned_data = super(TransactionForm, self).clean()
        if cleaned_data['amount_btc'] > 0. and cleaned_data['amount_eur'] > 0.:
            raise forms.ValidationError('Either BTC amount or fiat amount must be negative.')
        return cleaned_data

    def save(self, commit=True, *args, **kwargs):
        instance = super(TransactionForm, self).save(commit=False, *args, **kwargs)
        # store input data in integer format
        instance.amount_btc_satoshi = int(round(self.cleaned_data['amount_btc'] * 1e8))
        instance.amount_eur_milicent = int(round(self.cleaned_data['amount_eur'] * 1e5))
        # provide convenient amounts
        instance.amount_btc = instance.amount_btc_satoshi / 1e8
        instance.amount_eur = instance.amount_eur_milicent / 1e5
        instance.is_bid = instance.amount_btc_satoshi > 0
        instance.price_per_btc = -1. * instance.amount_eur / instance.amount_btc
        if commit:
            instance.save()
        return instance

    class Meta:
        model = Transaction
        fields = ['date', 'amount_btc', 'amount_eur']

现在添加新的transaction按预期工作is_bid并正确设置其他dependend字段。但是，编辑现有条目会导致仅更新一个字段。例如。即使price_per_btc是amount_eur_milicent也不会更改amount_eur和# File: views.py @login_required def transaction_add(request): form = TransactionForm(request.POST) if form.is_valid(): transaction = form.save(commit=False) transaction.user = request.user transaction.save() else: messages.error(request, ';'.join('{}: {}'.format(key, value) for key, value in form.errors.items())) return redirect(request.POST['next']) @login_required def transaction_edit(request, id): transaction = Transaction.objects.get(id=id) form = TransactionForm(request.POST, instance=transaction) if form.is_valid(): transaction.save() else: messages.error(request, ';'.join('{}: {}'.format(key, value) for key, value in form.errors.items())) return redirect(request.POST['next'])：

instance.save(update_fields=None)

我试过了{{1}}，但它根本没有任何效果。想法？

Answer 1

事务实例不会以这种方式修改，您应该显式调用form.save（）（导致表单实际包含已更改的数据）

transaction = Transaction.objects.get(id=id)
form = TransactionForm(request.POST, instance=transaction)
if form.is_valid():
    form.save()

您不会创建新对象，只需编辑现有对象，因为对象主键未更改

覆盖ModelForm.save不会更新所有受影响的字段

1 个答案: