Validating custom fields in Django models

Michael Zippo

Syntax —

 field_name = models.Field (validators = [function 1, function 2])

Explanation to validating Django custom fields

Illustration of validators using an example. Consider a project named pythonengineering that has an application named geeks .

Refer to the following articles to check how to create a project and an app in Django.

How to Create a Basic Project using MVT in Django?

How to Create an App in Django?

Enter the following code into the models.py file of the geeks application. We’ll use CharField to experiment with all the margin variations.

from django.db import models

from django.db.models import Model

# Create your models here.

class GeeksModel (Model):

geeks_mail = models.CharField (

max_length = 200 ,

)

We will now apply a custom validation so that the above field is validated for Google Mail IDs only. Create a function that takes an argument named value . Now you can apply any type of operation to the value. so let’s check if our function value contains @ gmail.com to check for Google Mail IDs only.

       from   django.db   import   models 
   # import validationerror  
   from   django.core.exceptions   import   ValidationError 
   
  # create a validator function  
   def   validate_geeks_mail (value): 
   if   "@ gmail.com "  in   value: 
     return   value 
   else  :  
   raise   ValidationError (  "This field accepts mail id of google only"  ) 
   
   
  # Create your models here.  
   class   GeeksModel (models.Model): 
   geeks_mail   =   models.CharField (max_length   =   200  )

Now let’s add this function as a validator in our field. Note that one validator function can be used for multiple fields at the same time.

from django.db import models

# import validationerror

from django.core.exceptions import ValidationError

# create a validator function

def validate_geeks_mail (value):

if "@ gmail.com" in value:

return value

else :

raise ValidationError ( "This field accepts mail id of google only" )

# Create your models here.

class GeeksModel (models.Model):

geeks_mail = models.CharField (

max_length = 200 ,

validators = [validate_geeks_mail]

)

Let’s try creating an instance without gmail.com and see if our check or not. Please note that after every change in models.py you need to run makemigrations and wrap the commands.
In your browser, go to at http:// localhost: 8000 / admin / geeks / geeksmodel / add / and enter "[email protected]".
Let’s check if it is saved in the database.

So the validation worked and this field can only accept email IDs ending in @ gmail. com. Thus, any kind of custom validation can be applied to value .