Serializers

ModelSerializer

from rest_framework import serializers
from .models import Post

class PostSerializer(serializers.ModelSerializer):
    class Meta:
        model = Post
        fields = '__all__'
        # fields = ['id', 'title']
        # exclude = ['slug']

Nested Serializers (Read-Only)

class CategorySerializer(serializers.ModelSerializer):
    class Meta:
        model = Category
        fields = ['id', 'name']

class PostSerializer(serializers.ModelSerializer):
    category = CategorySerializer(read_only=True)

    class Meta:
        model = Post
        fields = ['id', 'title', 'category']

Field-Level Validation

class PostSerializer(serializers.Serializer):
    def validate_title(self, value):
        if 'django' not in value.lower():
            raise serializers.ValidationError("Title must contain 'Django'")
        return value

Object-Level Validation

class PostSerializer(serializers.Serializer):
    def validate(self, data):
        if data['is_published'] and not data['published_at']:
            raise serializers.ValidationError("Published posts must have a date")
        return data

SerializerMethodField (Computed Fields)

class PostSerializer(serializers.ModelSerializer):
    content_length = serializers.SerializerMethodField()

    def get_content_length(self, obj):
        return len(obj.content)

    class Meta:
        model = Post
        fields = ['title', 'content_length']

Custom Field Source

class PostSerializer(serializers.ModelSerializer):
    author_name = serializers.CharField(source='author.username', read_only=True)

    class Meta:
        model = Post
        fields = ['title', 'author_name']

Writable Nested Serializers

class PostSerializer(serializers.ModelSerializer):
    category = CategorySerializer()

    def create(self, validated_data):
        category_data = validated_data.pop('category')
        category, _ = Category.objects.get_or_create(**category_data)
        return Post.objects.create(category=category, **validated_data)