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django - 将子对象与Django中每个实例的父对象相关联？

问题描述

我有两个模型，一个Invoice模型和一个Expense模型。创建发票后，用户应该能够添加发票的所有费用。一旦创建了发票 - 这些费用应该以某种方式“检查”，因此新发票不会添加相同的费用。我需要对费用实例进行某种形式的检查，说“已开票”之类的。不完全确定如何仅使用..set.filter(...)查询集我的两个模型如下所示：

费用模型


class Expense(Model):
    cost = DecimalField(blank=True, null=True, max_digits=10, decimal_places=2)
    project = ForeignKey(Project, on_delete=CASCADE)
    user = ForeignKey(User, on_delete=CASCADE) 
    billable = BooleanField(default=False)
    expense_date = DateField()
    date_created = DateTimeField(auto_now_add=True)
    invoice = ForeignKey("finances.Invoice", blank=True, null=True, on_delete=SET_NULL, help_text="Optionally link this to an existing invoice")

发票型号

class Invoice(Model):
    issue_date = DateField(default=now)
    due_date = DateField()
    project = ForeignKey(Project, on_delete=CASCADE)
    amount = DecimalField(blank=True, null=True, max_digits=100, decimal_places=2)
    include_expenses = BooleanField(default=False, help_text='Check this box to include all expenses that are within the invoice billable date range')
    billable_start = DateField(help_text="Logged hours start date")
    billable_end = DateField(help_text="Logged hours end date")

我尝试在 Expense 模型上添加一个查询集，如下所示：

    def get_billable_expenses(self):
        """Getting all expenses for selected billable period"""
        start_week = self.get_start_isoweek()
        end_week = self.get_end_isoweek()
        return self.project.expense_set.filter(
            expense_date__gte=self.billable_start, 
            expense_date__lte=self.billable_end,
            billable=True,
            invoice=self.id
        )

然后添加一个在保存发票时触发的信号：

@receiver(post_save, sender=Invoice)
def prepare_calculation_data(sender, instance=None, created=False, **kwargs):
    if created:
        expenses_to_add = []
        for expense in instance.get_billable_expenses():
            expense.invoice = instance
            expenses_to_add.append(expense)
        Expense.objects.bulk_update(expenses_to_add, ['invoice'])

不知道如何处理这个问题 - 我想我会通过检查费用是否已经有与之相关的发票来解决它 - 如果没有 - 将其包含在新创建的发票中（如上get_billable_expenses()所示），但这意味着不会有新的费用永远不会被添加，因为该invoice字段不会为空

关于如何解决它的任何建议？

标签： djangodjango-modelsdjango-forms

解决方案

我通过在我的Invoice模型上使用两种方法来解决它。一种查询未开票的费用：

    def get_billable_expenses(self):
        """Getting all expenses for selected billable period"""
        start_week = self.get_start_isoweek()
        end_week = self.get_end_isoweek()
        return self.project.expense_set.filter(
            expense_date__gte=self.billable_start, 
            expense_date__lte=self.billable_end,
            status='approved',
            billable=True,
            invoice__isnull=True
        )

然后在我的模板中显示这些费用：

    def get_linked_expenses(self):
        return self.project.expense_set.filter(
            invoice=self.id
        )

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