Stuck with Calculated feild

[eankomah]

Hi all am stuck at getting total_price Calculated in my model

class inventory(models.Model):

    def __str__(self):

        return self.name

    category = models.ForeignKey(Category, null=True, on_delete = models.SET_NULL)

    Supplier = models.ForeignKey(Supplier, null=True, on_delete = models.SET_NULL)

    product = models.ForeignKey(Product, null=True, on_delete = models.SET_NULL)

    quantity = models.FloatField()

    unit_price = models.FloatField()

    total_price = models.FloatField(total=('unit_price' * 'quantity'))

    selling_price = models.FloatField()

    date_created = models.DateTimeField(auto_now_add=True) 

Thanks

[dr neyx de godlove]

hi there you can create another method for that class that calculates the total as

@property

def get_total_price(self):

     total_price = self.unit_price * self.quantity

     return total_price

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[Kasper Laudrup]

Hi eankomah,

Completely unrelated, but:>     unit_price = models.FloatField()
Don't use floats for money. It will give you all kinds of problems with
rounding errors etc.

Assuming this is just a hobby project, it's probably fine, but otherwise
consider looking into something like:

https://github.com/django-money/django-money

Just an advice.

Kind regards,

Kasper Laudrup

[Harish Thiyagharajan]

I think you mailed me instead of mailing someone

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[Kasper Laudrup]

Hi Harish,

On 23/09/2020 11.27, Harish Thiyagharajan wrote:
> I think you mailed me instead of mailing someone
>

No. If you look at the mail header, you can see this was sent to the
django-users mailing list.

Kind regards,

Kasper Laudrup

[Frederic Salvetat]

Hi Eankomah,

You have several solution depending upon your need:

 

Le mercredi 23 septembre 2020 07:24:05 UTC+2, eankomah a écrit :
Hi all am stuck at getting total_price Calculated in my model
 
class inventory(models.Model):
    def __str__(self):
        return self.name

  ...

    total_price = models.FloatField(total=('unit_price' * 'quantity'))

  ...
Thanks

 

First dr neyx de godlove answer is the more elegant if you do not need a dedicated db field.

You just need to remove the 'get_' prefix  in get_total_price :

 

    @property

    def total_price(self):

        total_price = self.unit_price * self.quantity

        return total_price

 

(@dr neyx de godlove, thank I learned the use of property in django trying you solution)

 

Then if you really need a dedicated field, create it and override the save method in your model :

    total_price = models.FloatField()

 

    def save(self, *args, **kwargs):

        #change total_price

        # Transaction.save(update_fields['total_price'])

        self.total_price = self.unit_price * self.quantity

        super(Inventory, self).save(*args, **kwargs)

Best Regards

--

Frédéric Salvetat 

[Frederic Salvetat]

Hi Eankomah,

You have several solutions depending upon your need:

>Le mercredi 23 septembre 2020 07:24:05 UTC+2, eankomah a écrit :

>Hi all am stuck at getting total_price Calculated in my model

>

>class inventory(models.Model):

>    def __str__(self):

>        return self.name

>  ...

>    total_price = models.FloatField(total=('unit_price' * 'quantity'))

>  ...

>Thanks

First dr neyx de godlove's answer is the more elegant if you do not need a dedicated db field.

You just need to remove the 'get_' prefix  in get_total_price :

    @property

    def total_price(self):

        total_price = self.unit_price * self.quantity

        return total_price

(@dr neyx de godlove, thank I learned the use of property in django trying you solution)

Then if you really need a dedicated field, create it and override the save method in your model :

    total_price = models.FloatField()

    def save(self, *args, **kwargs):

        #change total_price

        # Transaction.save(update_fields['total_price'])

        self.total_price = self.unit_price * self.quantity

        super(Inventory, self).save(*args, **kwargs)

Best Regards

--

Frédéric Salvetat