HiddenField in serializers – Django REST Framework

In Django REST Framework the very concept of Serializing is to convert DB data to a datatype that can be used by javascript. Every serializer comes with some fields (entries) which are going to be processed. For example if you have a class with name Employee and its fields as Employee_id, Employee_name, is_admin, etc. Then, you would need AutoField, CharField and BooleanField for storing and manipulating data through Django. Similarly, serializer also works with same principle and has fields that are used to create a serializer. 
This article revolves around HiddenField in Serializers in Django REST Framework.
 

HiddenField

HiddenField is a field class that does not take a value based on user input, but instead takes its value from a default value or callable.
Syntax –  

field_name = serializers.HiddenField(*args, **kwargs)

Example – 
For example, to include a field that always provides the current time as part of the serializer validated data, you would use the following: 

modified = serializers.HiddenField(default=timezone.now)

The HiddenField class is usually only needed if you have some validation that needs to run based on some pre-provided field values, but you do not want to expose all of those fields to the end user.
 

How to use HiddenField in Serializers ?

To explain the usage of HiddenField, let’s use the same project setup from – How to Create a basic API using Django Rest Framework ?. 
Now that you have a file called serializers in your project, let’s create a serializer with HiddenField as the fields. 

Now let us create some objects and try serializing them and check if they are actually working, Run, –  

Python manage.py shell

Now, run following python commands in the shell 

# import everything from serializers
>>> from apis.serializers import *

# create a object of type Geeks
>>> obj = Geeks("Naveen", 999)

# serialize the object
>>> serializer = GeeksSerializer(obj)

# print serialized data
>>> serializer.data
{'name': 'Naveen'}

Here is the output of all these operations on terminal – 

Validation on HiddenField

Note that prime motto of these fields is to impart validations, such as HiddenField validates the data to hidden object only. Let’s check if these validations are working or not – 

# Create a dictionary and add values
>>> data = {}
>>> data['name'] = "Naveen"

# dictionary created
>>> data
{'name': 'Naveen'}

# deserialize the data
>>> serializer = GeeksSerializer(data=data)

# check if data is valid
>>> serializer.is_valid()
True

# check the errors
>>> serializer.errors
{}

Here is the output of these commands which clearly shows data valid even if hidden argument was not provided and it defaults to 1 – 

Advanced concepts

Validations are part of Deserialization and not serialization. As explained earlier, serializing is process of converting already made data into another data type, so there is no requirement of these default validations out there. Deserialization requires validations as data needs to be saved to database or any more operation as specified. So if you serialize data using these fields that would work.
 

Core arguments in serializer fields

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