Overwrite Django model __init__ method

问题

The Ingredient model of my Django project has an IntegerField which declares if this ingredient stock is managed by weight, units, or litters.

Although the database has its integer value I have to display its name. And instead of looping over every ingredient and setting its value, I thought it was better to overwrite the __init__ method of the Python class, but I don't get how.

models.py:

class Ingredient(models.Model):
    def __init__(self):
        super(Ingredient, self).__init__()
        if self.cost_by == 1:
            self.cost_by = 'Units'
        elif self.cost_by == 2:
            self.cost_by = 'Kilograms'
        elif self.cost_by == 3:
            self.cost_by = 'Litters'
#...etc...

So far I tried with this, but I'm getting the following error:

__init__() takes 1 positional argument but 0 were given

What argument should I provide?

回答1:

If you define choices on a field that contains the value to name mapping then you will get a select field rendered in any ModelForm for that field and you will get a method generated on the model to get the display name for the selected value get_<field_name>_display()

class Ingredient(models.Model):

    COST_BY_CHOICES = (
        (1, 'Units'),
        (2, 'Kilograms'),
        (3, 'Litters'),
    )

    cost_by = models.IntegerField(choices=COST_BY_CHOICES)

Used like this

ingredient = Ingredient(cost_by=1)
print(ingredient.get_cost_by_display())

回答2:

class Ingredient(models.Model):
     cost_by = .....
     def __str__(self): 
         if self.cost_by == 1: 
             self.cost_by = 'Units' 
         elif self.cost_by == 2: 
             self.cost_by = 'Kilograms' 
         elif self.cost_by == 3: 
             self.cost_by = 'Litters' 
         return self.cost

回答3:

The problem I find here is that you did not pass *args and **kwargs to the Models's __init__() and to the super's __init__()

class Ingredient(models.Model):
    def __init__(self, *args, **kwargs):
        super(Ingredient, self).__init__(*args, **kwargs)
        # etc

来源：https://stackoverflow.com/questions/60481894/overwrite-django-model-init-method

标签

python

django

class

model

init