CODEWITHSUNDEEP
django
Pape Madialy Diaw
Pape Madialy Diaw

Reputation: 35

why am I getting a none value in my method inside of my model with nested if?

I'm new in django trying to do a project of management of a small restaurant, in my consummation model,I have attributes that are foreign keys, and the date of consummation, now I try to calculate the sum of those attributes in a method inside the model by returning the total.

I tried 

class Consommation(models.Model):
    entree = models.ForeignKey(Entree, models.CASCADE, verbose_name="L'entree", null=True, blank=True)
    food = models.ForeignKey(Meals, models.CASCADE, verbose_name='Plat de resistance', null=True, blank=True)
    dessert = models.ForeignKey(Dessert, models.CASCADE, verbose_name='Dessert', null=True, blank=True)
    boisson = models.ForeignKey(Boisson, models.CASCADE, verbose_name='Boisson', null=True, blank=True)
    autres = models.ForeignKey(Autres, models.CASCADE, verbose_name='Snacks', null=True, blank=True)
    consomme_le = models.DateTimeField(default=timezone.now, editable=False)

class Facture(models.Model):
    consommation = models.OneToOneField(Consommation, models.CASCADE, null=True, blank=True,
                                        verbose_name='Facture')
    fait_le = models.DateField(default=timezone.now, editable=False)
    is_regle = models.BooleanField(default=False, verbose_name='Est regle')
    initials_caissier = models.CharField(max_length=5, verbose_name='Initiales du Caissier')

    def __str__(self):
        return 'Facture du :' + ' ' + str(self.fait_le)

    def get_absolute_url(self):
        return reverse('clients:facture_detail', kwargs={'pk': self.pk})

    def net_a_payer(self):
        if self.consommation:
            if not self.consommation.entree:
                self.consommation.entree.price = int(0)
                if not self.consommation.food:
                    self.consommation.food.price = int(0)
                    if not self.consommation.dessert:
                        self.consommation.dessert.price = int(0)
                        if not self.consommation.boisson:
                            self.consommation.boisson.price = int(0)
                            if not self.consommation.autres:
                                self.consommation.autres.price = int(0)
                                return self.consommation.entree.price + self.consommation.food.price + self.consommation.dessert.price + self.consommation.boisson.price + self.consommation.autres.price

net_a_payer: means the total sum to pay

I expect the result to be the sum of the attibutes instead of returning "None"

Upvotes: 2

Views: 38

Answers (1)

willeM_ Van Onsem
willeM_ Van Onsem

Reputation: 476557

If a function does not explicitly return something, it will return None. So your function will here only return a value in case all the conditions in this cascade of conditions hold.

That being said, you make things too complex, you can simply define a helper function, and sum up the prices:

class Facture(models.Model):

    # ...

    @staticmethod
    def get_price(item, _default=0):
        if item:
            return item.price
        return _default

    def net_a_payer(self):
        get_price = Facture.get_price
        con = self.consummation
        return get_price(con.entree) + get_price(con.food) + get_price(con.dessert) + get_price(con.boisson) + get_price(con.autres)

You might however want to consider remodeling this. For example making a general model "expense", and adding a category to it. That way, you can easily sum on the database level.

Upvotes: 2

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