Question

I have a model with a many-to-many field like this:

class BillingMonth(models.Model):
    month = models.IntegerField(min=1, max=12)

class BillingCycle(models.Model):
    description = models.CharField()
    months_billed = models.ManyToManyField(BillingMonth)

Each BillingCycle (monthly, quarterly, etc) will get billed in one or more months. The rental equipment model looks like this:

class RentalEquipment(models.Model):
    description = models.CharField()
    billing_cycle = models.ForeignKey(BillingCycle)

How do I find all RentalEquipment that should be billed on a given month? This doesn’t seem to work:

billing_month = BillingMonth(month=8)
RentalEquipment.objects.filter(billing_cycle__months_billed=billing_month)

Alternatively, is having a ManyToMany relationship overkill for the BillingCycle model? Is there a better way to include an array of dates?

Answer 1

It looks like I can break out the query like so:

billing_month = BillingMonth(month=8)
billing_cycles = Billing_cycle.objects.filter(months_billed=billing_month)
equipment_needing_billing = RentalEquipment.objects.filter(billing_cycle__in=billing_cycles)