How do i save many to many fields objects using django rest framework

Question

I have three models Blogs, Posted, Tags. In Blogs model I have fields 'postedin' as foreign key to Posted model and 'tags' as manytomany fields to Tags model.

models.py:

class Posted(models.Model):
    name = models.CharField(_('Posted In'),max_length=255, unique=True)

class Tags(models.Model):
    name = models.CharField(_('Tag Name'),max_length=255, unique=True)

class Blogs(models.Model):
    author = models.ForeignKey(CustomUser)
    title=models.CharField(max_length=100)
    postedin=models.ForeignKey(Posted)
    tags= models.ManyToManyField(Tags)
    content = models.TextField()
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

views.py:

class BlogViewSet(viewsets.ModelViewSet):
    queryset=Blogs.objects.order_by('-created_at')
    serializer_class= BlogsSerializer

def get_permissions(self):
    if self.request.method in permissions.SAFE_METHODS:
        return (permissions.AllowAny(),)
    return (permissions.IsAuthenticated(),IsAuthorOfBlog())

def perform_create(self,serializer):

    serializer.save(author=self.request.user)

    return super(BlogViewSet,self).perform_create(serializer)

serializers.py:

class TagsSerializer(serializers.ModelSerializer):
    class Meta:
        model = Tags

        fields = ('pk','name')
        read_only_fields=('pk','name')

class PostedSerializer(serializers.ModelSerializer):
    class Meta:
        model = Posted

        fields = ('pk','name')
        read_only_fields=('pk','name')

class BlogsSerializer(serializers.ModelSerializer):
    author = AccountSerializer(read_only=True,required=False)
    tags=TagsSerializer(read_only=True,many=True)
    tags_id = serializers.PrimaryKeyRelatedField(queryset=Tags.objects.all(), write_only=True)
    postedin = PostedSerializer(read_only=True)
    postedin_id = serializers.PrimaryKeyRelatedField(queryset=Posted.objects.all(), write_only=True)

    class Meta:
        model = Blogs

        fields = ('pk','author','title','tags','tags_id','postedin','postedin_id','content','created_at','updated_at')
        read_only_fields=('pk','created_at','updated_at')


    def get_validation_exclusions(self, *args, **kwargs):
        exclusions = super(BlogsSerializer, self).get_validation_exclusions()

        return exclusions + ['author']
    def create(self, validated_data):
        postedin = validated_data.pop('postedin_id')
        tags = validated_data.pop('tags_id')
        blogs = Blogs.objects.create(tags=tags,postedin=postedin, **validated_data)
        return blogs

Request sent:

{title: "nvnbv", postedin_id: "1", tags_id: ["2", "5", "1", "4"], content: "nmvmvjm"}

response receive:

{tags_id: ["Incorrect type. Expected pk value, received list."]}

I am beginner in Django-rest-framework.How to solve this error.

Thanks in advance !

Have you tried with serializers.PrimaryKeyRelatedField(queryset=Tags.objects.all(), write_only=True, many=True)? — Abdulafaja
– Abdulafaja, Commented Sep 9, 2016 at 6:44
@Abdulafaja getting error "'tags' is an invalid keyword argument for this function" — Deep 3015
– Deep 3015, Commented Sep 9, 2016 at 7:01
@Abdulafaja. after applying your suggestion . In 'def create(self, validated_data)' function — Deep 3015
– Deep 3015, Commented Sep 9, 2016 at 7:18
docs.djangoproject.com/es/1.10/topics/db/examples/many_to_many you cannot associate ManyToMany field before the Blogs is created — Abdulafaja
– Abdulafaja, Commented Sep 9, 2016 at 7:35

Deep 3015 · Accepted Answer · 2016-09-09 07:38:02Z

thanks @Abdulafaja for your suggestion.

Finally I got solution

BlogsSerializer should be

class BlogsSerializer(serializers.ModelSerializer):
    author = AccountSerializer(read_only=True,required=False)
    tags=TagsSerializer(read_only=True,many=True)
    tags_id = serializers.PrimaryKeyRelatedField(queryset=Tags.objects.all(), write_only=True,many=True)
    postedin = PostedSerializer(read_only=True)
    postedin_id = serializers.PrimaryKeyRelatedField(queryset=Posted.objects.all(), write_only=True)

    class Meta:
        model = Blogs

        fields = ('pk','author','title','tags','tags_id','postedin','postedin_id','content','created_at','updated_at')
        read_only_fields=('pk','created_at','updated_at')


    def get_validation_exclusions(self, *args, **kwargs):
        exclusions = super(BlogsSerializer, self).get_validation_exclusions()

        return exclusions + ['author']
    def create(self, validated_data):
        postedin = validated_data.pop('postedin_id')
        tags = validated_data.pop('tags_id')
        blogs = Blogs.objects.create(postedin=postedin, **validated_data)
        for tg in tags:
            blogs.tags.add(tg)
        return blogs

Gm Zulkar Nine · Accepted Answer · 2022-10-25 07:49:54Z

2

Instead of loop, you can simply use this line blogs.tags.add(*tags)

def create(self, validated_data):
    postedin = validated_data.pop('postedin_id')
    tags = validated_data.pop('tags_id')
    blogs = Blogs.objects.create(postedin=postedin, **validated_data)
    blogs.tags.add(*tags)
    return blogs

edited Oct 25, 2022 at 7:49

answered Dec 20, 2021 at 5:23

Gm Zulkar Nine

213 bronze badges

1 Comment

Jota Over a year ago

Even better, blogs.tags.set(tags) because is a CREATION not an UPDATE.

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