Django Form初始值不在呈现上起作用

我有一个‘Transaction’模型和ModelForm来创建一个:

class Transaction(models.Model):
    """ Invoice model.
     Represents a basic income/outcome transaction. """
    
    title = models.CharField(max_length=32, verbose_name="Title")
    category = models.ForeignKey(Category, related_name="transactions", on_delete=models.CASCADE, null=True, blank=True)
    operation = models.CharField(max_length=8, choices=OPERATION_TYPE, verbose_name="operation")
    value = models.DecimalField(max_digits=14, decimal_places=2, verbose_name="value")
    currency = models.CharField(max_length=3, choices=CURRENCY_CHOICE, verbose_name="currency")
    comment = models.CharField(max_length=255, null=True, blank=True)
    date_created = models.DateField(auto_now_add=True, blank=True, null=True)

    class Meta:
        verbose_name_plural = "Transactions"
        ordering = ["-date_created"]

class NewInvoiceForm(forms.ModelForm):
    category = TreeNodeChoiceField(queryset=Category.objects.all())

    class Meta:
        model = Transaction
        fields = ("title", "category", "operation", "value", "currency")
        help_texts = {
            "operation": _("Money spent/received. For expenses use a negative value.")
        }

我有一个与每个用户链接的首选项模型来存储设置:

class Config(models.Model):
    """ Represents user's preferences. """
    
    user = models.OneToOneField(CustomUser, related_name="config", on_delete=models.CASCADE)
    currency = models.CharField(max_length=3, choices=CURRENCY_CHOICE, default=DEFAULT_SETTINGS["currency"])
    language = models.CharField(max_length=56, choices=LANGUAGE_CHOICE, default=DEFAULT_SETTINGS["language"])

    class Meta:
        verbose_name = "config"
        verbose_name_plural = "configs"

我试图从Config模型获得用户的货币作为Transaction创建表单的初始值.但初始值永远不会呈现.

我的观点是:

def create_transaction_view(request):
    if request.method == "POST":
        form = NewInvoiceForm(
            request.POST,
            instance=request.user
        )
        if form.is_valid():
            new_invoice = Transaction(**form.cleaned_data)
            # retrieving user's currency preference for further converting if income is different from base currency
            user_currency = request.user.config.currency
            # performing currency conversion to maintain consistent data for statistic and analyse
            if user_currency != new_invoice.currency:
                transaction_converted_value = CurrencyExchangeManager.currency_converter(
                    value=new_invoice.value,
                    exchange_to=user_currency,
                    base=new_invoice.currency
                )
                new_invoice.value = transaction_converted_value
                new_invoice.currency = user_currency
            new_invoice.save()
        return HttpResponseRedirect(request.META.get('HTTP_REFERER', "/"))

我总是得到一个‘破折号’字段作为初始 Select . 感谢您对此主题的任何建议.