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25 / 29Django REST API DevelopmentHardPython - Django Framework

Custom Validation in DRF Serializers

from rest_framework import serializers
from django.core.validators import MinValueValidator

class EmployeeSerializer(serializers.Serializer):
    name = serializers.CharField(max_length=100)
    salary = serializers.DecimalField(max_digits=10, decimal_places=2, validators=[MinValueValidator(0)])
    department = serializers.CharField(max_length=50)
    email = serializers.EmailField()
    
    def validate_salary(self, value):
        if value > 1000000:
            raise serializers.ValidationError("Salary cannot exceed 1000000")
        return value
    
    def validate(self, data):
        if data['department'] == 'Management' and data['salary'] < 50000:
            raise serializers.ValidationError("Management employees must earn at least 50000")
        return data

  1. A salary of 999999 will pass field validation but fail object validation if department is 'Management' with salary below 50000. A salary of -100 will fail MinValueValidator.

  2. The validate_salary method will be called before the MinValueValidator, allowing it to accept negative salaries if they're below 1000000.

  3. The object-level validate method cannot access individual field values like data['salary'] directly.

  4. EmailField does not perform automatic validation; you must add a custom validator to check email format.

Show answer & explanation

Correct answer

A salary of 999999 will pass field validation but fail object validation if department is 'Management' with salary below 50000. A salary of -100 will fail MinValueValidator.

Explanation

Field-level validation (validate_salary) checks individual fields, while object-level validation (validate) checks cross-field constraints. Validators are applied before custom validation methods.

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All 29 Django REST API Development questions

  1. 1.What is the primary purpose of Django REST Framework (DRF)?
  2. 2.What is a Serializer in Django REST Framework?
  3. 3.Which decorator is used to convert a regular Django view into an API view in DRF?
  4. 4.What is the purpose of ViewSets in Django REST Framework?
  5. 5.Which class should be inherited to create a basic API view in DRF?
  6. 6.What is the default authentication method in Django REST Framework?
  7. 7.How do you register URLs for ViewSets in Django REST Framework?
  8. 8.What does the status module in DRF provide?
  9. 9.Which permission class allows only authenticated users to access an API endpoint?
  10. 10.What is the Response class used for in Django REST Framework?
  11. 11.Scenario:
  12. 12.What will be the output of the following code snippet?
  13. 13.Scenario:
  14. 14.What is the difference between ModelSerializer and Serializer in Django REST Framework?
  15. 15.Identify the bug in the following code snippet:
  16. 16.How do you implement pagination in a Django REST Framework API?
  17. 17.Scenario:
  18. 18.What is the purpose of the queryset attribute in a ViewSet?
  19. 19.Scenario:
  20. 20.What will be the output of this code snippet?
  21. 21.Understanding DRF Serializers and Nested Relationships
  22. 22.DRF Viewsets and Router Configuration Scenario
  23. 23.Authentication and Permissions in DRF
  24. 24.Pagination and Filtering in DRF Scenario
  25. 25.Custom Validation in DRF Serializers
  26. 26.Status Codes and Exception Handling in DRF
  27. 27.Throttling and Rate Limiting Scenario
  28. 28.Request and Response Cycle with Middleware
  29. 29.Advanced Serializer Optimization and Performance