Re: Calculated Fields

[Mike Dewhirst]

On 11/04/2022 2:48 pm, tech george wrote:

Hello Mike,


reorder_level * unit_price + quantity

Unfortunately it's not calculating the fields as I wanted, instead it's calculating as below;

Try using brackets like this ...

self.total_price = (self.reorder_level + self.quantity) * self.unit_price

Although I might use an error preventer. Perhaps like this ...

if self.unit_price and (self.reorder_level or self.quantity):

    self.total_price = (self.reorder_level + self.quantity) * self.unit_price

Which is wrong because I'm getting less amount.

Regards

On Mon, 11 Apr 2022, 01:56 Mike Dewhirst, <mi...@dewhirst.com.au> wrote:









    -------- Original message --------
    From: tech george <techgeor...@gmail.com>
    Date: 11/4/22 03:50 (GMT+10:00)
    To: django-users@googlegroups.com
    Subject: Calculated Fields

    Hello,

    I am trying to calculate fields directly from a model but no luck.
    I want to get total_price from quantity, reoder_level and unit
    price. My code is abelow, Please advise.

    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)
        reorder_level = models.IntegerField(default='0', blank=True,
    null=True)


        def save(self, *args, **kwargs):
            self.total_price = self.quantity + self.reorder_level *
    self.unit_price
            super(Stock, self).save(*args, **kwargs)


    What am i my doing wrong

    If it was my code, I would extract the calculation into a model
    method and call it from the save method as you are doing.

    That would make it easier to unit-test and perhaps discover that
    there should be parens around the addition.

    You also need to call save on your model to execute the code.

    Apart from that, at first glance your code should work.



    Regards,


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