Custom Validators of Model Field

In Django, you can define custom validators for model fields to enforce specific validation rules for the data stored in those fields. Here are five examples of custom validators for model fields:

 

1. Custom Email Validator:

   Suppose you want to ensure that an email field contains a valid email address format. You can create a custom validator like this:

 

from django.core.exceptions import ValidationError
from django.core.validators import validate_email

def validate_custom_email(value):
       try:
           validate_email(value)
       except ValidationError:
           raise ValidationError('Invalid email format')


email = models.EmailField(validators=[validate_custom_email])

 

   In this example, the `validate_custom_email` function checks if the provided value is a valid email address using Django's built-in `validate_email` function and raises a `ValidationError` if it's not valid.

 

2. Custom File Extension Validator:

 

   You can create a custom validator to ensure that file uploads have specific file extensions:

 

 

from django.core.exceptions import ValidationError
import os

def validate_file_extension(value):
       ext = os.path.splitext(value.name)[1]
       allowed_extensions = ['.jpg', '.jpeg', '.png', '.gif']

       if ext.lower() not in allowed_extensions:
           raise ValidationError('Only JPG, JPEG, PNG, and GIF files are allowed.')

uploaded_file = models.FileField(upload_to='uploads/', validators=[validate_file_extension])

 

   This validator checks the file extension of an uploaded file and raises a `ValidationError` if it's not in the list of allowed extensions.

 

3. Custom Password Validator:

 

   Suppose you want to enforce specific password strength criteria:

 

from django.core.exceptions import ValidationError

def validate_password_strength(value):
       if len(value) < 8:
           raise ValidationError('Password must be at least 8 characters long')
       if not any(char.isnumeric() for char in value):
           raise ValidationError('Password must contain at least one digit')

password = models.CharField(max_length=100, validators=[validate_password_strength])

 

   This validator checks the length and presence of numeric characters in the password and raises a `ValidationError` if the criteria are not met.

 

4. Custom URL Validator:

 

   Ensure that a URL field contains valid URLs:

 

from django.core.exceptions import ValidationError
from django.core.validators import URLValidator

def validate_custom_url(value):
       validator = URLValidator()
       try:
           validator(value)
       except ValidationError:
           raise ValidationError('Invalid URL format')

website_url = models.URLField(validators=[validate_custom_url])

 

   In this example, the `validate_custom_url` function uses Django's `URLValidator` to check if the provided URL is valid.

 

5. Custom Age Validator:

 

   Suppose you want to ensure that an age field contains a reasonable age value:

 

from django.core.exceptions import ValidationError

def validate_age(value):
       if value < 0 or value > 120:
           raise ValidationError('Invalid age value')

age = models.IntegerField(validators=[validate_age])

 

   This validator checks that the age is within a reasonable range (0 to 120) and raises a `ValidationError` if it's not.

 

These examples demonstrate how you can create custom validators for Django model fields to enforce specific validation rules on your data. Custom validators allow you to tailor the validation logic to your application's requirements.