Serializers

Serializer Function Field

SerializerFunctionField is very similar to SerializerMethodField. except you pass a function instead of a method to the field.

You should use SerializerFunctionField when you have to include the same functionality in several serializers.

Example

Let's take a look to example when you need to return whether authenticated user follows the other user.

Here is the comparison of code using method field and function field approaches

SerializerFunctionField

from rest_framework import serializers
from drf_dog.serializers import SerializerFunctionField


def get_is_following(obj, context):
    return obj.followers.filter(pk=context['request'].user.pk).exists()

class UserSerializer(serializers.ModelSerializer):
    is_following = SerializerFunctionField(function=get_is_following)

    class Meta:
        model = User
        fields = ('id', 'username', 'is_following')

SerializerMethodField

from rest_framework import serializers


class UserSerializer(serializers.ModelSerializer):
    is_following = serializers.SerializerMethodField()

    class Meta:
        model = User
        fields = ('id', 'username', 'is_following')

    def get_is_following(self, obj):
        return obj.followers.filter(
            pk=self.context['request'].user.pk
        ).exists()

This is very useful when you have several serializers relying on get_is_following.

For example,

from rest_framework import serializers
from drf_dog.serializers import SerializerFunctionField

from my_project.utils import get_is_following


class AutocompleteUserSerializer(serializers.ModelSerializer):
    is_following = SerializerFunctionField(function=get_is_following)

    class Meta:
        model = User
        fields = ('id', 'username', 'is_following')


class RetrieveUserSerializer(serializers.ModelSerializer):
    is_following = SerializerFunctionField(function=get_is_following)

    class Meta:
        model = User
        fields = ('id', 'username', 'email', 'is_active', 'avatar', 
                  'is_following')

So, above is some sort of solution to code duplication .