django - 如何在models.py中的save方法中获取内联对象

我有类发票，它(简化)具有以下属性:

class Invoice(models.Model)
    number = models.CharField(verbose_name="Number", max_length=16)
    issue_date = models.DateTimeField(verbose_name="Issue date", default=datetime.now)
    total = models.FloatField(verbose_name="Total", blank=True, null=True)

然后，我有类 InvoiceLine，它表示发票可以包含的一行/几行:

class InvoiceLine(models.Model):
    invoice = models.ForeignKey(Invoice, verbose_name="Invoice")
    description = models.CharField(verbose_name="Description", max_length=64)
    line_total = models.FloatField(verbose_name="Line total")

InvoiceLine 是 Invoice 的内联，我想要实现的是，当在管理员中有人保存发票及其行(一个或多个)时，计算发票总额。我试图通过覆盖方法保存来做到这一点:

class Invoice(models.Model)
    number = models.CharField(verbose_name="Number", max_length=16)
    issue_date = models.DateTimeField(verbose_name="Issue date", default=datetime.now)
    total = models.FloatField(verbose_name="Total", blank=True, null=True)

    def save(self, *args, **kwargs):
         invoice_lines = InvoiceLine.objects.filter(invoice=self.id)
         self.total = 0
         for line in invoice_lines:
             self.total=self.total+line.line_total
         super(Invoice, self).save(*args, **kwargs)

问题是，当我在 InvoiceLine 中添加元素时，第一次保存并调用函数时，内联(InvoiceLine)中的新元素尚未存储，因此当我执行 InvoiceLine.objects.filter(invoice=self.id) 时，它​​们没有被考虑在内.因此，唯一有效的方法是节省两次。
我也试过:

def save(self, *args, **kwargs):
    super(Invoice, self).save(*args, **kwargs)
    invoice_lines = InvoiceLine.objects.filter(invoice=self.pk)
    self.total = 0
    for line in invoice_lines:
        self.total=self.total+line.line_total
    super(Invoice, self).save(*args, **kwargs)

但有相同的结果。任何想法？
提前致谢!

最佳答案

最后我在 Change object after saving all inlines in Django Admin 的帖子上找到了它，它对我帮助很大。关键是在 admin.py 中，我已经有了我的类 InvoiceHeaderAdmin(admin.ModelAdmin) ，但是我不得不放置三个函数，以便在保存所有内联后修改 total 属性:这样，查询 invoice_lines = InvoiceLine.objects.filter(invoice_header=obj.pk) 不能正常工作以前，现在它完美无缺。周二功能 InvoiceHeaderAdmin 已如下:

class InvoiceHeaderAdmin(admin.ModelAdmin):
    inlines = [InvoiceLineInline]
    list_filter = ('format_line','issue_date',)
    list_display = ('number','organization','issue_date','total',)
    fields = ('format_line','organization','issue_date',)

    #the following functions are for calculating the total price of the invoice header based on the lines
    def response_add(self, request, new_object):
        obj = self.after_saving_model_and_related_inlines(new_object)
        return super(InvoiceHeaderAdmin, self).response_add(request, obj)

    def response_change(self, request, obj):
        obj = self.after_saving_model_and_related_inlines(obj)
        return super(InvoiceHeaderAdmin, self).response_change(request, obj)

    def after_saving_model_and_related_inlines(self, obj):

        invoice_lines = InvoiceLine.objects.filter(invoice_header=obj.pk)

        obj.total = 0
        for line in invoice_lines:
            obj.total=obj.total+line.line_total
        obj.save()
        return obj

线索是最后一个函数，其中所有内联都已保存，现在我可以从对象(发票)计算属性并修改它。