Field Validations and Built-In Fields - Django Models
Field validations in Django help make sure the data you enter into your database is correct and follows certain rules. Django automatically checks the data based on the type of field you use, so you don’t have to write extra code to validate it yourself.
Django provides built-in validations for every field type, making it easier for developers to enforce rules without writing extra code.
How Do Built-in Validations Work
Each type of field in Django has its own built-in checks. For example:
- IntegerField only accepts whole numbers.
- CharField is for text and limits how long the text can be.
- DateField checks that the value is a valid date.
If you try to save wrong data, Django will give an error and won’t let the data be saved.
Demonstration of Built-in Validation
Consider a project named geeksforgeeks having an app named geeks.
Refer to the following articles to check how to create a project and an app in Django.
Enter the following code into models.py file of geeks app.
from django.db import models
class GeeksModel(models.Model):
geeks_field = models.IntegerField()
def __str__(self):
return str(self.geeks_field)
After running makemigrations and migrate on Django and rendering above model, let us try to create an instance using string "GfG is Best".
You can see in the admin interface, one can not enter a string in an IntegerField. Similarly, every field has its own validations.
Extra Built-in Validations You Can Use
Django has choices of fields for almost every data you want to store in database such as IntegerField for integer and CharField for strings. But there are some built-in validations which you can apply on these fields too.
For example, unique=True will limit the entries of a particular field to unique entries. Below is a list of built-in validations you can use for your field to make more changes.
| Field Options | Description |
|---|---|
| Null | If True, Django will store empty values as NULL in the database. Default is False. |
| Blank | If True, the field is allowed to be blank. Default is False. |
| db_column | The name of the database column to use for this field. If this isn’t given, Django will use the field’s name. |
| Default | The default value for the field. This can be a value or a callable object. If callable it will be called every time a new object is created. |
| help_text | Extra “help” text to be displayed with the form widget. It’s useful for documentation even if your field isn’t used on a form. |
| primary_key | If True, this field is the primary key for the model. |
| editable | If False, the field will not be displayed in the admin or any other ModelForm. They are also skipped during model validation. Default is True. |
| error_messages | The error_messages argument lets you override the default messages that the field will raise. Pass in a dictionary with keys matching the error messages you want to override. |
| help_text | Extra “help” text to be displayed with the form widget. It’s useful for documentation even if your field isn’t used on a form. |
| verbose_name | A human-readable name for the field. If the verbose name isn’t given, Django will automatically create it using the field’s attribute name, converting underscores to spaces. |
| validators | A list of validators to run for this field. See the validators documentation for more information. |
| Unique | If True, this field must be unique throughout the table. |
Read Next: Custom Field Validations in Django Models
