Django: Rest Framework Serialization Cheat Sheet

Serializers allow complex data like querysets and model instances to be converted to native Python datatypes that can then be easily rendered into JSON, XML, and other formats.

Using ModelSerializer class:

Suppose we wanted to create a PostSerializer for our example Post model and CommentSerializer for our Comment model.

class PostSerializer(serializers.ModelSerializer):

    class Meta:
        model = Post
        fields = ('id', 'title', 'text', 'created')
        
        
class CommentSerializer(serializers.ModelSerializer):

    class Meta:
        model = Comment
        fields = ('post', 'user', 'text')

Or also you could use exclude to exclude certain fields from being seialized. ModelSerializer has default implementations for the create() and update() methods.

Nested Serialization

By default, instances are serialized with primary keys to represent relationships. To get nested serialization we could use, General or Explicit methods.

General

Using depth parameter.

class CommentSerializer(serializers.ModelSerializer):

    class Meta:
        model = Comment
        fields = '__all__'
        depth = 2

Explicit

Yuo can also define and nest serializers within eachother…

class CommentSerializer(serializers.ModelSerializer):
    post = PostSerializer()
    
    class Meta:
        model = Comment
        fields = '__all__'

So here, the comment’s post field (how we named it in models.py) will serialize however we defined it in PostSerializer.

HyperlinkedModelSerializer

This makes your web API a lot more easy to use (in browser) and would be a nice feature to add.

Let’s say we wanted to see the comments that every post has in each of the Post instances of our API.

With HyperlinkedModelSerializer, instead of having nested primary keys or nested fields, we get a link to each individual Comment (URL).

class PostSerializer(serializers.HyperlinkedModelSerializer):

    class Meta:
        model = Post
        fields = ('id', 'title', 'text', 'created', 'comments')
        read_only_fields = ('comments',)

Note: without the read_only_fields, the create form for Posts would always require a comments input, which doesn’t make sense (comments on a post are normally made AFTER the post is created).

Another way of hyperlinking is just adding a HyperlinkedRelatedField definition to a normal serializer.

class PostSerializer(serializers.ModelSerializer):
    comments = serializers.HyperlinkedRelatedField(many=True, view_name='comment-detail', read_only=True)
    
    class Meta:
        model = Post
        fields = ('id', 'title', 'text', 'created', 'comments')

Dynamically modifying fields in the serializer

This makes your web API a lot more easy for extract limited number of parameter in response. Let’s say you want to set which fields should be used by a serializer at the point of initialization.

Just copy below code and past it in your serliazer file

class DynamicFieldsModelSerializer(serializers.ModelSerializer):

    def __init__(self, *args, **kwargs):
        # Don't pass the 'fields' arg up to the superclass
        fields = kwargs.pop('fields', None)

        # Instantiate the superclass normally
        super(DynamicFieldsModelSerializer, self).__init__(*args, **kwargs)

        if fields is not None:
            # Drop any fields that are not specified in the `fields` argument.
            allowed = set(fields)
            existing = set(self.fields.keys())
            for field_name in existing - allowed:
                self.fields.pop(field_name)

Extend DynamicFieldsModelSerializer from your serializer class

class UserSerializer(DynamicFieldsModelSerializer):
    class Meta:
        model = User
        fields = ('id', 'username', 'email')

Mention the fields name inside fields

UserSerializer(user, fields=('id', 'email'))

Here, you will get only id and email from serializer instead of all.

Leave a Reply

Your email address will not be published.