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Django Restframework Serializers Overview

19 Oct 2019 | Django DRF

Introduction

참조 : Django Rest Framework Serialization

Serializer class

The first thing we need to get started on our Web API is to provide a way of serializing and deserializing the snippet instances into representations such as json.

Web API를 시작할 때 알아야 할 부분은 모델 인스턴스를 json과 같은 형식으로 표현할 줄 알아야 합니다. 이를 직렬화 비직렬화 라고 합니다.

from rest_framework import serializers
from snippets.models import Snippet, LANGUAGE_CHOICES, STYLE_CHOICES


class SnippetSerializer(serializers.Serializer):
    id = serializers.IntegerField(read_only=True)
    title = serializers.CharField(required=False, allow_blank=True, max_length=100)
    code = serializers.CharField(style={'base_template': 'textarea.html'})
    linenos = serializers.BooleanField(required=False)
    language = serializers.ChoiceField(choices=LANGUAGE_CHOICES, default='python')
    style = serializers.ChoiceField(choices=STYLE_CHOICES, default='friendly')

    def create(self, validated_data):
        """
        Create and return a new `Snippet` instance, given the validated data.
        """
        return Snippet.objects.create(**validated_data)

    def update(self, instance, validated_data):
        """
        Update and return an existing `Snippet` instance, given the validated data.
        """
        instance.title = validated_data.get('title', instance.title)
        instance.code = validated_data.get('code', instance.code)
        instance.linenos = validated_data.get('linenos', instance.linenos)
        instance.language = validated_data.get('language', instance.language)
        instance.style = validated_data.get('style', instance.style)
        instance.save()
        return instance

Dealing with multiple objects

Dealing with multiple objects

The Serializer class can also handle serializing or deserializing lists of objects. To serialize a queryset or list of objects instead of a single object instance, you should pass the many=True flag when instantiating the serializer. You can then pass a queryset or list of objects to be serialized.

object를 serialize, deserialize하는것 이외에도 쿼리셋도 같은 작업을 할 수 있다. many=True 옵션을 주면된다.

queryset = Book.objects.all()
serializer = BookSerializer(queryset, many=True)
serializer.data
# [
#     {'id': 0, 'title': 'The electric kool-aid acid test', 'author': 'Tom Wolfe'},
#     {'id': 1, 'title': 'If this is a man', 'author': 'Primo Levi'},
#     {'id': 2, 'title': 'The wind-up bird chronicle', 'author': 'Haruki Murakami'}
# ]

ModelSerializers

ModelSerializer

  • An automatically determined set of fields.
  • Simple default implementations for the create() and update() methods.
class SnippetSerializer(serializers.ModelSerializer):
    class Meta:
        model = Snippet
        fields = [‘id’, ‘title’, ‘code’, ‘linenos’, ‘language’, ‘style’]

ModelSerializer는 serializer에서 직접 작성해줘야하는 save, update같은 함수를 자동으로 만들어준다. 또한 메타클레스에 필드명만 입력해줘도 자동으로 serializer에서 정의하는 필드들을 완성해준다.

Often you’ll want serializer classes that map closely to Django model definitions. The ModelSerializer class provides a shortcut that lets you automatically create a Serializer class with fields that correspond to the Model fields. TheModelSerializerclass is the same as a regularSerializerclass, except that:

  • It will automatically generate a set of fields for you, based on the model.
  • It will automatically generate validators for the serializer, such as unique_together validators.
  • It includes simple default implementations of .create() and .update(). Declaring a ModelSerializer looks like this:

모델시리얼라이저는 Serializer와 동일한 기능을하고 추가적으로 편리한 기능을 제공한다. 모델만 입력해주면 자동으로 모든 필드에 대해 처리를 해준다. 하지만 웬만하면 사용하지 않을것이다. 성능의 저하를 가져온다.

Writing regular Django views using our Serializer

@csrf_exempt
def snippet_list(request):
    """
    List all code snippets, or create a new snippet.
    """
    if request.method == 'GET':
        snippets = Snippet.objects.all()
        serializer = SnippetSerializer(snippets, many=True)
        return JsonResponse(serializer.data, safe=False)

    elif request.method == 'POST':
        data = JSONParser().parse(request)
        serializer = SnippetSerializer(data=data)
        if serializer.is_valid():
            serializer.save()
            return JsonResponse(serializer.data, status=201)
        return JsonResponse(serializer.errors, status=400)

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