Models Culculations

[tech george]

Hello,

Please help with the below, I am trying to get dispense_quantity from Dispense Model and subtract it from the quantity on Stock Model.

Then after that get something like this;

@property

def closing_stock(self):

      return (self.quantity - self. quantity_issued  )

class Stock(models.Model):
    unit_price = models.DecimalField(max_digits=10, decimal_places=2, default='0', blank=True, null=True)
    quantity = models.IntegerField(default='0', blank=True, null=True)
    total_price = models.DecimalField(max_digits=10, decimal_places=2, default=1)
    total_stock = models.IntegerField(default='0', blank=True, null=True)
    receive_quantity = models.IntegerField(default='0', blank=True, null=True)
    reorder_level = models.IntegerField(default='0', blank=True, null=True)
    reorder_price = models.DecimalField(max_digits=10, decimal_places=2, default='0', blank=True, null=True)

    def __str__(self):
        return str(self.drug_name)

    @property
    def total_price(self):
        return (self.quantity + self.reorder_level) * self.unit_price

    @property
    def total_stock(self):
        return (self.quantity + self.reorder_level)

    @property
    def reorder_stock(self):
        return (self.reorder_level * self.reorder_price)

class Dispense(models.Model):
    nurse = models.ForeignKey(Pharmacist, on_delete=models.CASCADE, null=True)
    patient_id = models.ForeignKey(Patients, on_delete=models.DO_NOTHING, null=True)
    drug_id = models.ForeignKey(Stock, on_delete=models.SET_NULL, null=True, blank=False)
    dispense_quantity = models.PositiveIntegerField(default='1', blank=False, null=True)
    taken = models.CharField(max_length=300, null=True, blank=True)