How to install

pip install djangorestframework-serializer-mixins

How to use

Assume you have a Post model:

# testapp/models.py
from django.conf import settings
from django.db import models


class Post(models.Model):
    user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE, related_name='posts')
    title = models.CharField(max_length=128)
    body = models.TextField()
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    def __str__(self):
        return self.title

    class Meta:
        ordering = ['-created_at']

Write DynamicPostSerializer with DynamicFieldsMixin:

# testapp/serializers.py
from rest_framework import serializers

from rest_framework_serializer_mixins import DynamicFieldsMixin

from .models import Post


class DynamicPostSerializer(DynamicFieldsMixin, serializers.ModelSerializer):
    class Meta:
        model = Post
        fields = (
            'body',
            'created_at',
            'id',
            'title',
            'updated_at',
            'user',
        )
        read_only_fields = (
            'id',
            'user',
        )

Now, you can define fields and read_only_field like this:

>>> from django.contrib.auth.models import User
>>> from testapp.models import Post
>>> from testapp.serializers import DynamicPostSerializer
>>> user = User.objects.create_user('user', 'user@email.com', '123456')
>>> post = Post.objects.create(user=user, title='My Title', body='My Body')
>>> data = DynamicPostSerializer(post) # return fields and read_only_fields from Meta
>>> serializer = DynamicPostSerializer(post) # return fields and read_only_fields from Meta
>>> serializer.data
{'body': 'My Body', 'created_at': '2018-02-14T14:15:29.772209Z', 'id': 1, 'title': 'My Title', 'updated_at': '2018-02-14T14:15:29.772312Z', 'user': 1}
>>> serializer = DynamicPostSerializer(post, fields=('title', 'body')) # return only title and body fields
>>> serializer.data
{'body': 'My Body', 'title': 'My Title'}
>>> serializer = DynamicPostSerializer(post, read_only_fields=('title', 'body'), data={'title': 'New Title', 'body': 'New Body'}) # set title and body as read_only_fields
>>> serializer.is_valid()
True
>>> serializer.save()
<Post: My Title>
>>> serializer.data
{'body': 'My Body', 'created_at': '2018-02-14T14:15:29.772209Z', 'id': 1, 'title': 'My Title', 'updated_at': '2018-02-14T14:19:14.838001Z', 'user': 1} # title and body don't change