Django get id from model

100domino 0
Viewed 24

how can I get id from just created model so that it can be used in item_name column. I was thinking about sth like this:

class Items(models.Model):
    item_id = models.AutoField(primary_key=True)
    item_name = models.CharField(
        max_length=100, default="Item #{}".format(item_id)
    )
django-models django
1 Answers

you can use in default callable object, something, like function, but not the lambda:

set_name(obj):
    return f'Item #{obj}'  # this is not work for new object

class Items(models.Model):
    # item_id = models.AutoField(primary_key=True) you dont need it, it will be created automatically
     item_name = models.CharField(
        max_length=100, default=set_name.format(item_id)
    )

One problem - this is not work for new object, you always will receive None. But your item_name is static, that's why you can made a property, for example:

class Items(models.Model):
    # item_id = models.AutoField(primary_key=True) you don't need it, it will be created automatically
     name = models.CharField(
        max_length=100, null=false, blank=true, default='')
     
     @property         
     def item_name(self):
         return f'{self.name or 'Item'} #{self.pk or "New object"}'

Other possibility is - to override __str__ or __repr__:

class Items(models.Model):
    # item_id you don't need it, it will be created automatically
    # item_name you don't need it too

    def __str__(self):
        return  f'Item #{self.pk}'

    def __repr__(self):
        return f'{self}'

    @property         
    def item_name(self):
        return f'{self}'
Maxim Danilov0
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