I have a simple DRF REST API that I want to use to create blog articles. I want to be able to add tags to those blog articles so users can search tags and see related articles. However, the tags may not exist yet. I have created an Article Model with a ForeignKey field to a Tag Model like this:
class Tag(models.Model):
name = models.CharField(max_length=32)
def _str__(self):
return self.name
class Meta:
ordering = ('name',)
class Article(models.Model):
title = models.CharField(max_length=256)
author = models.ForeignKey(User, on_delete=models.CASCADE)
content = models.TextField()
date = models.DateTimeField(auto_now_add=True)
tags = models.ForeignKey(Tag, on_delete=models.CASCADE, blank=True, default=None)
def __str__(self):
return self.title
class Meta:
ordering = ('date', 'id')
Ideally what I want is to be able to POST a new Article with a set of tags, and if any of the tags don't exist, create them in the DB. However, as it is currently, the tags need to already exist to be added to the Article. Visually, DRF shows this as a dropdown that is populated with pre-existing tags:
How can I add or create multiple Tags from my Article API endpoint?
EDIT: As requested, I've added my views.py
views.py:
from api.blog.serializers import ArticleSerializer, TagSerializer
from rest_framework import viewsets
# /api/blog/articles
class ArticleView(viewsets.ModelViewSet):
queryset = Article.objects.all()
serializer_class = ArticleSerializer
# /api/blog/tags
class TagView(viewsets.ModelViewSet):
queryset = Tag.objects.all()
serializer_class = TagSerializer
For completeness, here are my serializers from my REST API's serializers.py.
serializers.py:
class ArticleSerializer(serializers.ModelSerializer):
class Meta:
model = Article
fields = '__all__'
class TagSerializer(serializers.ModelSerializer):
class Meta:
model = Tag
fields = '__all__'
urls.py:
from rest_framework import routers
router = routers.DefaultRouter()
router.register('articles', views.ArticleView)
router.register('tags', views.TagView)
urlpatterns = [
path('', include(router.urls)),
]
Overriding the create() method of the serializer as
class ArticleSerializer(serializers.ModelSerializer):
tags = serializers.CharField()
class Meta:
model = Article
fields = '__all__'
def create(self, validated_data):
tag = validated_data.pop('tags')
tag_instance, created = Tag.objects.get_or_create(name=tag)
article_instance = Article.objects.create(**validated_data, tags=tag_instance)
return article_instance
Okay, thanks to #JPG for their help. This is what I've ended up with. It allows users to add space delimited tags into a CharField on the /api/blog/article endpoint. When a POST request is performed, the tags are split on spaces, get_or_create()d (for this to work I needed to make Tag.name the primary key), and then added to the Article with article.tags.set(tag_list). As #JPG and #Martins suggested, a ManyToManyField() was the best way to do this.
Here is my full code:
serializers.py:
class ArticleSerializer(serializers.ModelSerializer):
class TagsField(serializers.CharField):
def to_representation(self, tags):
tags = tags.all()
return "".join([(tag.name + " ") for tag in tags]).rstrip(' ')
tags = TagsField()
class Meta:
model = Article
fields = '__all__'
def create(self, validated_data):
tags = validated_data.pop('tags') # Removes the 'tags' entry
tag_list = []
for tag in tags.split(' '):
tag_instance, created = Tag.objects.get_or_create(name=tag)
tag_list += [tag_instance]
article = Article.objects.create(**validated_data)
print(tag_list)
article.tags.set(tag_list)
article.save()
return article
class TagSerializer(serializers.ModelSerializer):
class Meta:
model = Tag
fields = '__all__'
Note that I had to create a custom TagField() and override to_representation(). This is because if I used a regular serializer.CharField() tags were displayed as: "Blog.tag.None" instead of the tag values, like this:
models.py:
class Tag(models.Model):
name = models.CharField(max_length=32, primary_key=True)
def __str__(self):
return self.name
class Meta:
ordering = ('name',)
class Article(models.Model):
title = models.CharField(max_length=256)
author = models.ForeignKey(User, on_delete=models.CASCADE)
content = models.TextField()
date = models.DateTimeField(auto_now_add=True)
tags = models.ManyToManyField(Tag)
def __str__(self):
return self.title
class Meta:
ordering = ('date', 'id')
Related
I have an blog website and my visitors can also comment on my blog posts. Each blog post have multiple comment and I want to show those comment under my each single blog post. Assume Blog1 have 10 comment so all 10 comment will be show under Blog1
here is my code:
models.py
class Blog(models.Model):
blog_title = models.CharField(max_length=200, unique=True)
class Comment(models.Model):
name = models.CharField(max_length=100)
email = models.EmailField(max_length=100)
comment = models.TextField()
blog = models.ForeignKey(Blog, on_delete=models.CASCADE)
Serializer.py
class CommentSerializer(serializers.ModelSerializer):
class Meta:
model = Comment
fields = '__all__'
class BlogSerializer(serializers.ModelSerializer):
class Meta:
model = Blog
exclude = ("author", "blog_is_published")
lookup_field = 'blog_slug'
extra_kwargs = {
'url': {'lookup_field': 'blog_slug'}
}
views.py:
class BlogViewSet(viewsets.ModelViewSet):
queryset = Blog.objects.all().order_by('-id')
serializer_class = BlogSerializer
pagination_class = BlogPagination
lookup_field = 'blog_slug'
You can access comments list from blog object using comment_set attribute, so add comment_set field to your serializer:
class BlogSerializer(serializers.ModelSerializer):
comment_set = CommentSerializer(many=True)
class Meta:
model = Blog
exclude = ("author", "blog_is_published")
lookup_field = 'blog_slug'
extra_kwargs = {
'url': {'lookup_field': 'blog_slug'}
}
I'm trying to fetch related objects from below two models.
Following django models with ManyToManyField relationship.
Book
class Book(models.Model):
authors = models.ManyToManyField(
to=Author, verbose_name="Authors", related_name="books_author"
)
bookshelves = models.ManyToManyField(
to=Bookshelf, verbose_name="Bookshelf", related_name="books_shelves"
)
copyright = models.NullBooleanField()
download_count = models.PositiveIntegerField(blank=True, null=True)
book_id = models.PositiveIntegerField(unique=True, null=True)
languages = models.ManyToManyField(
to=Language, verbose_name=_("Languages"), related_name="books_languages"
)
Author
class Author(models.Model):
birth_year = models.SmallIntegerField(blank=True, null=True)
death_year = models.SmallIntegerField(blank=True, null=True)
name = models.CharField(max_length=128)
def __str__(self):
return self.name
class Meta:
verbose_name = _("Author")
verbose_name_plural = _("Author")
I have to fetch all the Auhtors with their related books. I have tried a lot of different ways none is working for me.
First way : using prefetch_related
class AuthorListAPIView(APIErrorsMixin, generics.ListAPIView):
serializer_class = AuthorSerializer
queryset = Author.objects.exclude(name__isnull=True)
def get_queryset(self):
auths = queryset.prefetch_related(Prefetch("books_author"))
Second way using related_name 'books_auhtor'
class AuthorListAPIView(APIErrorsMixin, generics.ListAPIView):
serializer_class = AuthorSerializer
queryset = Author.objects.exclude(name__isnull=True)
def get_queryset(self):
auths = queryset.books_author.all()
None of the above ways worked for me. I want to prepare a list of Authors and their associated books.
For ex:-
[{'Author1':['Book1','Book2'],... }]
Prefetching is not necessary, but can be used to boost efficiency, you can work with:
class AuthorListAPIView(APIErrorsMixin, generics.ListAPIView):
serializer_class = AuthorWithBooksSerializer
queryset = Author.objects.exclude(name=None).prefetch_related('books_author')
In the AuthorWithBooksSerializer, you can then add the data of the books, for example:
from rest_framework import serializers
class BookSerializer(serializers.ModelSerializer):
class Meta:
model = Book
fields = ('book_id', 'copyright')
class AuthorWithBooksSerializer(serializers.ModelSerializer):
books = BookSerializer(source='books_author', many=True)
class Meta:
model = Author
fields = ('name', 'books')
Here the books will use the BookSerializer and thus encode a list of dictionaries.
While you can use the name of the author as object key, I strongly advise against this: it makes the object less accessible since the keys are no longer fixed and if these contain spaces, it can also result in more trouble obtaining the value(s) associated with a given attribute name.
So I'm using Django and have a foreignkey field. Let me show you the model first.
class Book(models.Model):
objects = models.Manager()
title = models.CharField(max_length = 30)
author = models.CharField(max_length = 20)
class Content(models.Model):
objects = models.Manager()
source = models.ForeignKey("Book", related_name='book', on_delete=models.CASCADE)
key_line = models.CharField(max_length = 100, null=True)
I used serializer to load the api to my React front end. But then, the source field is displayed as integer, which probably is the id of Book model.
However what I want to do is load the title of each book in the source field.
Any advice?
FYI, other codes.
views.py
#api_view(['GET'])
def each_book(request, pk):
this_book = Content.objects.get(pk=pk)
serialized = ContentSerializer(this_book, context={'request':request})
return Response(serialized.data)
serializers.py
class ContentSerializer(serializers.ModelSerializer):
class Meta:
model = Content
fields = '__all__'
You could just pass book to the context field and call it like:
#api_view(['GET'])
def each_book(request, pk):
this_book = Content.objects.get(pk=pk)
serialized = ContentSerializer(this_book, context={'request':request, 'book': this_book})
return Response(serialized.data)
Then
class ContentSerializer(serializers.ModelSerializer):
book_title = serializers.SerializerMethodField()
class Meta:
model = Content
fields = '__all__'
def get_book_title(self, obj): # Note that obj is `content` in this case.
return self.context['book'].title
Make sure you include it in your fields too. Not sure if it works with __all__. If it doesn't, then just explicitly write all your fields out with the book_title field included.
I have a pair of parent/children relation models like:
class Post(models.Model):
title = models.TextField(null=True)
content = models.TextField(null=True)
author = models.TextField(null=True)
created_time = models.DateTimeField(null=True)
class Comment(models.Model):
content = models.TextField(null=True)
created_time = models.DateTimeField(null=True)
post = models.ForeignKey(Post, on_delete=models.CASCADE)
and the serializers are like:
class PostSerializer(serializers.ModelSerializer):
class Meta:
model = Post
fields = '__all__'
class CommentSerializer(serializers.ModelSerializer):
class Meta:
model = Comment
fields = '__all__'
and finally views:
class PostView(viewsets.ModelViewSet):
queryset = Post.objects.all()
serializer_class = PostSerializer
class CommentView(viewsets.ModelViewSet):
queryset = Comment.objects.all()
serializer_class = CommentSerializer
Now I want to created an API that returns a list of Posts, in which each Post will contain two additional fields, one be all_comments, and the other will be latest_comment. I understand this could be easily done in SQL using JOINs. I am new to Django. I wonder if there's any easy way to do it in Django. Thanks.
Hope this config works for you :)
class CommentPostSerializer(serializers.ModelSerializer): # New Serializer class
class Meta:
model = Comment
exclude = ('post',)
class PostSerializer(serializers.ModelSerializer):
all_comments = CommentPostSerializer(read_only=True, many=True, source='comment_set')
latest_comment = serializers.SerializerMethodField()
def get_latest_comment(self, post):
latest_comment = post.comment_set.last()
return CommentPostSerializer(latest_comment).data
class Meta:
model = Post
fields = '__all__'
I want to create a model (Source) with many-to-many relation to the another model (Tag) and create a Source objects without duplicating Tag instance in database.
Here is my models:
class Tag(models.Model):
name = models.CharField(max_length=50, null=False, default='source')
def __unicode__(self):
return self.name
class Source(models.Model):
title = models.CharField(max_length=200)
author = models.CharField(max_length=200)
language = models.CharField(max_length=50)
color = models.CharField(max_length=50, default='white')
isFile = models.BooleanField(default=False)
link = models.TextField(default='')
file = models.FileField(upload_to='uploads/', null=True)
tags = models.ManyToManyField('Tag')
class Meta:
ordering = ('title',)
Here is my serializers:
class TagSerializers(serializers.HyperlinkedModelSerializer):
class Meta:
model = Tag
fields = ('name',)
class SourceSerializers(serializers.ModelSerializer):
tags = TagSerializers(many=True)
class Meta:
model = Source
fields = ('title', 'author', 'language', 'color', 'isFile', 'link', 'file', 'tags')
def create(self, validated_data):
tags_data = validated_data.pop('tags')
source = Source.objects.create(**validated_data)
for tag in tags_data:
t = Tag.objects.create()
t.name = tag.get("name")
t.save()
source.tags.add(t)
source.save()
return source
But when I try to create Source object via http request - the object is created, but without any references to Tags. After some researching I found that validated_data in create(self, validated_data) doesn't contains "tags" field, also I found that validate function of TagSerializer not invoked at any time. What I'm doing wrong?
Use get_or_create method to create Tag object.
def create(self, validated_data):
tags_data = validated_data.pop('tags')
source = Source.objects.create(**validated_data)
for tag in tags_data:
name = tag.get("name")
t = Tag.objects.get_or_create(name=name)
t.save()
source.tags.add(t)
source.save()
return source
Seems the problem was in my requests, without many-to-many relation we can use form-data and all is good, but when we add mant-to-many relation we can't use form-data anymore and have to use only application\json