Associate child object with parent object per instance in Django? - django

Question

I've got two models, an Invoice model and an Expense model. Upon creating invoices, the user should be able to add all expenses for an invoice. Once an invoice has been created - these expenses should somehow be "checked" so a new invoice doesn't add the same expenses. I'd need some form of check on the expense instance saying "has been invoiced" or something. Not entirely sure how to proceed with only a ..set.filter(...) queryset My two models looks like this:
Expense model
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")
Invoice model
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")
I tried adding a queryset on the Expense model as such:
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
)
And then adding a signal that is triggered when an invoice is saved:
#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'])
Not sure how to handle this - I thought I'd solve it by checking if the expense already has an invoice tied to it - if not - include it in the newly created invoice (as seen in get_billable_expenses() above) but that means no new expenses will ever be added either as the invoicefield won't be empty
Any suggestions on how to solve it?

Answer 1

I solved it by having two methods on my Invoice model. One to query for un-invoiced expenses:
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
)
and then in my template showing those expenses as such:
def get_linked_expenses(self):
return self.project.expense_set.filter(
invoice=self.id
)