CODEWITHSUNDEEP
pythondjango
nathaner
nathaner

Reputation: 553

Reuse Primary Key in another Django model field

Is it possible to reference the primary key in another field in a Django model?

For example, let's say I want to have a field looking like BUG0001 corresponding to the entry with pk=1. What is the best way to achieve this?

I think it is best to keep the primary key as an integer as it is easier to deal with, and I guess formatting the primary key every time is not very effective.

Upvotes: 0

Views: 736

Answers (2)

ha-neul
ha-neul

Reputation: 3248

Yes you can.

class Product(models.Model):
     other= models.CharField(max_length=50, blank=True, null=True)

     def save(self, *args, **kwargs):
        self.another = "BUG%d" %(self.pk)
        super(Product, self).save(*args, **kwargs)

You can check out python string formatting.

Another way is to use @property docor @cached_propertydoc .

In your case, @cached_property may be better. property and cached_property will not be saved in database. but you can call it in your template as if this is another model field.

Obvious benefit of using property and cahced_property is that you will not need to save to db every time you need to save model.

from django.utils.functional import cached_property

class Product(models.Model):
     # since we want to have "another" as a property, you do not need to 
     # generate a field called "another"
     #another= models.CharField(max_length=50, blank=True, null=True)
      
     somefield = models.CharField(max_length=50, blank=True, null=True)
     
     @cached_property
     def another(self):
        return "BUG%d" %(self.pk)
        # not sure why the above string formatting not working for you.
        # you can simply do:
        return "BUG" + str(self.pk)

     def save(self, *args, **kwargs):
        super(Product, self).save(*args, **kwargs)

Upvotes: 0

Vishal Pandey
Vishal Pandey

Reputation: 359

Yes it possible and easy to do. Just do this

First make primary key from django.db import models class Fruit(models.Model): name = models.CharField(max_length=100,primary_key=True)

And then call it where you want as foreign key foreign= models.ForeignKey(Reporter, on_delete=models.CASCADE)

Upvotes: 1

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