DRF DAY 6

Hyperlinked Identity Field

Hyperlinked Identity Field is a field that represents the URL of the object itself. It is useful when you want to provide a link to the object in the API response.

Note: It is read-only field.

Implementation: Consider the following model:

from django.db import models
class Author(models.Model):
    name = models.CharField(max_length=100)
    email = models.EmailField()

    def __str__(self):
        return self.name

Now, we will create a serializer for this model using Hyperlinked Identity Field:

from rest_framework import serializers
from .models import Author
class AuthorSerializer(serializers.HyperlinkedModelSerializer):
    url = serializers.HyperlinkedIdentityField(
        view_name='author-detail',  # The name of the view that provides the detail of the author
        lookup_field='id'  # The field used to look up the object
    )
    class Meta:
        model = Author
        fields = ['id', 'name', 'email']  # 'url' is the Hyperlinked Identity Field

Now, we need to create a view for this serializer:

from rest_framework.views import APIView
from rest_framework.response import Response
from rest_framework import status
from .models import Author
from .serializers import AuthorSerializer
class AuthorView(APIView):
    def get(self, request, *args, **kwargs):
        authors = Author.objects.all()
        serializer = AuthorSerializer(authors,
                                     many=True,
                                    context={'request': request} # context is required to generate the full URL for the Hyperlinked Identity Field
                                    )
        return Response(serializer.data, status=status.HTTP_200_OK)

    def post(self, request, *args, **kwargs):
        serializer = AuthorSerializer(
            data=request.data,
            context={'request': request}  # context is required to generate the full URL for the Hyperlinked Identity Field
            )
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data, status=status.HTTP_201_CREATED)
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

Now, we need to create a URL for this view:

from django.urls import path
from .views import AuthorView,AuthorDetailView
urlpatterns = [
    path('authors/', AuthorView.as_view(), name='author-list'),
    path('authors/<int:id>/', AuthorDetailView.as_view(), name='author-detail'),  # Detail view for Hyperlinked Identity Field
]

The output of the API will look like this on /api/authors/:

[
    {
        "url": "http://localhost:8000/api/authors/1/",
        "id": 1,
        "name": "John Doe",
        "email": "[email protected]"
    },
    {
        "url": "http://localhost:8000/api/authors/2/",
        "id": 2,
        "name": "Kane Doe",
        "email": "[email protected]"
    }
]

Some Of the important points to note:

The url field is the Hyperlinked Identity Field that provides the URL of the author object.
The view_name parameter in the HyperlinkedIdentityField specifies the name of the view that provides the detail of the author.
The lookup_field parameter specifies the field used to look up the object. In this case, it is the id field.
The context parameter is required to generate the full URL for the Hyperlinked Identity Field. It should contain the request object.

Some of important field are: view_name: The name of the view that provides the detail of the object. lookup_field: The field used to look up the object. It can be any field in the model, not just the primary key.

Hyperlinked Related Field

Normally the relationship between two models is represented by a foreign key (Primary key related field) But sometimes we want to represent the relationship between two models by a URL. In that case, we can use Hyperlinked Related Field.

Implementation: Consider the following models:

from django.db import models
class Author(models.Model):
    name = models.CharField(max_length=100)
    email = models.EmailField()

    def __str__(self):
        return self.name

class Book(models.Model):
    title = models.CharField(max_length=100)
    author = models.ForeignKey(Author, related_name='books', on_delete=models.CASCADE)

    def __str__(self):
        return self.title

Now, we will create a serializer for the Book model using Hyperlinked Related Field:

from rest_framework import serializers
from .models import Book, Author

class AuthorSerializer(serializers.ModelSerializer):
    class Meta:
        model = Author
        fields = ['id', 'name', 'email']

class BookSerializer(serializers.ModelSerializer):
    author = serializers.HyperlinkedRelatedField(
        view_name='author-detail',  # The name of the view that provides the detail of the author
        lookup_field='id'  # The field used to look up the object
    )

    class Meta:
        model = Book
        fields = ['id', 'title', 'author']

Now, we need to create a view for this serializer:

from rest_framework.views import APIView
from rest_framework.response import Response
from rest_framework import status
from .models import Book
from .serializers import BookSerializer

class BookView(APIView):
    def get(self, request, *args, **kwargs):
        books = Book.objects.all()
        serializer = BookSerializer(books, many=True, context={'request': request})
        return Response(serializer.data, status=status.HTTP_200_OK)

    def post(self, request, *args, **kwargs):
        serializer = BookSerializer(data=request.data, context={'request': request})
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data, status=status.HTTP_201_CREATED)
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

Now, we need to create a URL for this view:

from django.urls import path
from .views import BookView, AuthorDetailView
urlpatterns = [
    path('books/', BookView.as_view(), name='book-list'),
    path('authors/<int:id>/', AuthorDetailView.as_view(), name='author-detail'),  # Detail view for Hyperlinked Related Field
]

The output of the API will look like this on /api/books/:

[
    {
        "id": 1,
        "title": "Book One",
        "author": "http://localhost:8000/api/authors/1/"
    },
    {
        "id": 2,
        "title": "Book Two",
        "author": "http://localhost:8000/api/authors/2/"
    }
]

Some of the important points to note:

The author field is the Hyperlinked Related Field that provides the URL of the author object.
The view_name parameter in the HyperlinkedRelatedField specifies the name of the view that provides the detail of the author.
The lookup_field parameter specifies the field used to look up the object. In this case, it is the id field.
The context parameter is required to generate the full URL for the Hyperlinked Related Field. It should contain the request object.

Some of important field are:

view_name: The name of the view that provides the detail of the related object.
lookup_field: The field used to look up the related object. It can be any field in the model, not just the primary key.
queryset: The queryset used for model instance lookups when validating the field input. Relationships must either set a queryset explicitly, or set read_only=True
many: If True, the field will accept a list of URLs. If False, it will accept a single URL. Default is False.
allow_null:If set to True, the field will accept values of None or the empty string for nullable relationships. Defaults to False.

Send requrest to save data like:

{
    "title": "Book Three",
    "author": "http://localhost:8000/api/authors/1/"
}

Hyperlinked Identity Field#

Hyperlinked Related Field#

Hyperlinked Identity Field

Hyperlinked Related Field