DRF Writable Nested
====================
[](https://codecov.io/gh/beda-software/drf-writable-nested)
[](https://pypi.python.org/pypi/drf-writable-nested)
[](https://pypi.python.org/pypi/drf-writable-nested)
This is a writable nested model serializer for Django REST Framework which
allows you to create/update your models with related nested data.
The following relations are supported:
- OneToOne (direct/reverse)
- ForeignKey (direct/reverse)
- ManyToMany (direct/reverse excluding m2m relations with through model)
- GenericRelation (this is always only reverse)
Requirements
============
- Python (3.8, 3.9, 3.10, 3.11, 3.12)
- Django (4.2, 5.0)
- djangorestframework (3.14+)
Installation
============
```
pip install drf-writable-nested
```
Usage
=====
For example, for the following model structure:
```python
from django.db import models
class Site(models.Model):
url = models.CharField(max_length=100)
class User(models.Model):
username = models.CharField(max_length=100)
class AccessKey(models.Model):
key = models.CharField(max_length=100)
class Profile(models.Model):
sites = models.ManyToManyField(Site)
user = models.OneToOneField(User, on_delete=models.CASCADE)
access_key = models.ForeignKey(AccessKey, null=True, on_delete=models.CASCADE)
class Avatar(models.Model):
image = models.CharField(max_length=100)
profile = models.ForeignKey(Profile, related_name='avatars', on_delete=models.CASCADE)
```
We should create the following list of serializers:
```python
from rest_framework import serializers
from drf_writable_nested.serializers import WritableNestedModelSerializer
class AvatarSerializer(serializers.ModelSerializer):
image = serializers.CharField()
class Meta:
model = Avatar
fields = ('pk', 'image',)
class SiteSerializer(serializers.ModelSerializer):
url = serializers.CharField()
class Meta:
model = Site
fields = ('pk', 'url',)
class AccessKeySerializer(serializers.ModelSerializer):
class Meta:
model = AccessKey
fields = ('pk', 'key',)
class ProfileSerializer(WritableNestedModelSerializer):
# Direct ManyToMany relation
sites = SiteSerializer(many=True)
# Reverse FK relation
avatars = AvatarSerializer(many=True)
# Direct FK relation
access_key = AccessKeySerializer(allow_null=True)
class Meta:
model = Profile
fields = ('pk', 'sites', 'avatars', 'access_key',)
class UserSerializer(WritableNestedModelSerializer):
# Reverse OneToOne relation
profile = ProfileSerializer()
class Meta:
model = User
fields = ('pk', 'profile', 'username',)
```
Also, you can use `NestedCreateMixin` or `NestedUpdateMixin` from this package
if you want to support only create or update logic.
For example, we can pass the following data with related nested fields to our
main serializer:
```python
data = {
'username': 'test',
'profile': {
'access_key': {
'key': 'key',
},
'sites': [
{
'url': 'http://google.com',
},
{
'url': 'http://yahoo.com',
},
],
'avatars': [
{
'image': 'image-1.png',
},
{
'image': 'image-2.png',
},
],
},
}
user_serializer = UserSerializer(data=data)
user_serializer.is_valid(raise_exception=True)
user = user_serializer.save()
```
This serializer will automatically create all nested relations and we receive a
complete instance with filled data.
```python
user_serializer = UserSerializer(instance=user)
print(user_serializer.data)
```
```python
{
'pk': 1,
'username': 'test',
'profile': {
'pk': 1,
'access_key': {
'pk': 1,
'key': 'key'
},
'sites': [
{
'pk': 1,
'url': 'http://google.com',
},
{
'pk': 2,
'url': 'http://yahoo.com',
},
],
'avatars': [
{
'pk': 1,
'image': 'image-1.png',
},
{
'pk': 2,
'image': 'image-2.png',
},
],
},
}
```
It is also possible to pass through values to nested serializers from the call
to the base serializer's `save` method. These `kwargs` must be of type `dict`. E g:
```python
# user_serializer created with 'data' as above
user = user_serializer.save(
profile={
'access_key': {'key': 'key2'},
},
)
print(user.profile.access_key.key)
```
```python
'key2'
```
Note: The same value will be used for all nested instances like default value but with higher priority.
Testing
=======
To run unit tests, run:
```bash
# Setup the virtual environment
python3 -m venv envname
source envname/bin/activate
pip install django
pip install django-rest-framework
pip install -r requirements.txt
# Run tests
py.test
```
Known problems with solutions
=============================
##### Validation problem for nested serializers with unique fields on update
We have a special mixin `UniqueFieldsMixin` which solves this problem.
The mixin moves` UniqueValidator`'s from the validation stage to the save stage.
If you want more details, you can read related issues and articles:
https://github.com/beda-software/drf-writable-nested/issues/1
http://www.django-rest-framework.org/api-guide/validators/#updating-nested-serializers
###### Example of usage:
```python
class Child(models.Model):
field = models.CharField(unique=True)
class Parent(models.Model):
child = models.ForeignKey('Child')
class ChildSerializer(UniqueFieldsMixin, serializers.ModelSerializer):
class Meta:
model = Child
class ParentSerializer(NestedUpdateMixin, serializers.ModelSerializer):
child = ChildSerializer()
class Meta:
model = Parent
```
Note: `UniqueFieldsMixin` must be applied only on serializer
which has unique fields.
###### Mixin ordering
When you are using both mixins
(`UniqueFieldsMixin` and `NestedCreateMixin` or `NestedUpdateMixin`)
you should put `UniqueFieldsMixin` ahead.
For example:
```python
class ChildSerializer(UniqueFieldsMixin, NestedUpdateMixin,
serializers.ModelSerializer):
```
##### Update problem for nested fields with form-data in `PATCH` and `PUT` methods
There is a special problem while we try to update any model object with nested fields
within it via `PUT` or `PATCH` using form-data we can not update it. And it complains
about fields not provided. So far, we came to know that this is also a problem in DRF.
But we can follow a tricky way to solve it at least for now.
See the below solution about the problem
If you want more details, you can read related issues and articles:
https://github.com/beda-software/drf-writable-nested/issues/106
https://github.com/encode/django-rest-framework/issues/7262#issuecomment-737364846
###### Example:
```python
# Models
class Voucher(models.Model):
voucher_number = models.CharField(verbose_name="voucher number", max_length=10, default='')
image = models.ImageField(upload_to="vouchers/images/", null=True, blank=True)
class VoucherRow(models.Model):
voucher = models.ForeignKey(to='voucher.Voucher', on_delete=models.PROTECT, verbose_name='voucher',
related_name='voucherrows', null=True)
account = models.CharField(verbose_name="fortnox account number", max_length=255)
debit = models.DecimalField(verbose_name="amount", decimal_places=2, default=0.00, max_digits=12)
credit = models.DecimalField(verbose_name="amount", decimal_places=2, default=0.00, max_digits=12)
description = models.CharField(verbose_name="description", max_length=100, null=True, blank=True)
# Serializers for these models
class VoucherRowSerializer(WritableNestedModelSerializer):
class Meta:
model = VoucherRow
fields = ('id', 'account', 'debit', 'credit', 'description',)
class VoucherSerializer(serializers.ModelSerializer):
voucherrows = VoucherRowSerializer(many=True, required=False, read_only=True)
class Meta:
model = Voucher
fields = ('id', 'participants', 'voucher_number', 'voucherrows', 'image')
```
Now if you want to update `Voucher` with `VoucherRow` and voucher image then you need to do it
using form-data via `PUT` or `PATCH` request where your `voucherrows` fields are nested field.
With the current implementation of the `drf-writable-nested` doesn't update it. Because it does
not support something like-
```text
voucherrows[1].account=1120
voucherrows[1].debit=1000.00
voucherrows[1].credit=0.00
voucherrows[1].description='Debited from Bank Account'
voucherrows[2].account=1130
voucherrows[2].debit=0.00
voucherrows[2].credit=1000.00
voucherrows[2].description='Credited to Cash Account'
```
This is not supported at least for now. So, we can achieve the result in a different way.
Instead of sending the array fields separately in this way we can convert the whole fields
along with values in a `json` string like below and set it as value to the field `voucherrows`.
```json
"[{\"account\": 1120, \"debit\": 1000.00, \"credit\": 0.00, \"description\": \"Debited from Bank Account\"}, {\"account\": 1130, \"debit\": 0.00, \"credit\": 1000.00, \"description\": \"Credited to Cash Account\"}]"
```
Now it'll be actually sent as a single field value to the application for the field `voucherrows`.
From your `views` you need to parse it like below before sending it to the serializer-
```python
class VoucherViewSet(viewsets.ModelViewSet):
serializer_class = VoucherSerializer
queryset = serializer_class.Meta.model.objects.all().order_by('-created_at')
def update(self, request, *args, **kwargs):
request.data.update({'voucherrows': json.loads(request.data.pop('voucherrows', None))})
return super().update(request, *args, **kwargs)
```
Now, you'll get the `voucherrows` field with data in the right format in your serializers.
Similar approach will be also applicable for generic views for django rest framework
Authors
=======
2014-2022, beda.software
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"description": "DRF Writable Nested\n====================\n\n[](https://codecov.io/gh/beda-software/drf-writable-nested)\n[](https://pypi.python.org/pypi/drf-writable-nested)\n[](https://pypi.python.org/pypi/drf-writable-nested)\n\nThis is a writable nested model serializer for Django REST Framework which\nallows you to create/update your models with related nested data.\n\nThe following relations are supported:\n- OneToOne (direct/reverse)\n- ForeignKey (direct/reverse)\n- ManyToMany (direct/reverse excluding m2m relations with through model)\n- GenericRelation (this is always only reverse)\n\nRequirements\n============\n\n- Python (3.8, 3.9, 3.10, 3.11, 3.12)\n- Django (4.2, 5.0)\n- djangorestframework (3.14+)\n\nInstallation\n============\n\n```\npip install drf-writable-nested\n```\n\nUsage\n=====\n\nFor example, for the following model structure:\n```python\nfrom django.db import models\n\n\nclass Site(models.Model):\n url = models.CharField(max_length=100)\n\n\nclass User(models.Model):\n username = models.CharField(max_length=100)\n\n\nclass AccessKey(models.Model):\n key = models.CharField(max_length=100)\n\n\nclass Profile(models.Model):\n sites = models.ManyToManyField(Site)\n user = models.OneToOneField(User, on_delete=models.CASCADE)\n access_key = models.ForeignKey(AccessKey, null=True, on_delete=models.CASCADE)\n\n\nclass Avatar(models.Model):\n image = models.CharField(max_length=100)\n profile = models.ForeignKey(Profile, related_name='avatars', on_delete=models.CASCADE)\n```\n\nWe should create the following list of serializers:\n\n```python\nfrom rest_framework import serializers\nfrom drf_writable_nested.serializers import WritableNestedModelSerializer\n\n\nclass AvatarSerializer(serializers.ModelSerializer):\n image = serializers.CharField()\n\n class Meta:\n model = Avatar\n fields = ('pk', 'image',)\n\n\nclass SiteSerializer(serializers.ModelSerializer):\n url = serializers.CharField()\n\n class Meta:\n model = Site\n fields = ('pk', 'url',)\n\n\nclass AccessKeySerializer(serializers.ModelSerializer):\n\n class Meta:\n model = AccessKey\n fields = ('pk', 'key',)\n\n\nclass ProfileSerializer(WritableNestedModelSerializer):\n # Direct ManyToMany relation\n sites = SiteSerializer(many=True)\n\n # Reverse FK relation\n avatars = AvatarSerializer(many=True)\n\n # Direct FK relation\n access_key = AccessKeySerializer(allow_null=True)\n\n class Meta:\n model = Profile\n fields = ('pk', 'sites', 'avatars', 'access_key',)\n\n\nclass UserSerializer(WritableNestedModelSerializer):\n # Reverse OneToOne relation\n profile = ProfileSerializer()\n\n class Meta:\n model = User\n fields = ('pk', 'profile', 'username',)\n```\n\nAlso, you can use `NestedCreateMixin` or `NestedUpdateMixin` from this package\nif you want to support only create or update logic.\n\nFor example, we can pass the following data with related nested fields to our\nmain serializer:\n\n```python\ndata = {\n 'username': 'test',\n 'profile': {\n 'access_key': {\n 'key': 'key',\n },\n 'sites': [\n {\n 'url': 'http://google.com',\n },\n {\n 'url': 'http://yahoo.com',\n },\n ],\n 'avatars': [\n {\n 'image': 'image-1.png',\n },\n {\n 'image': 'image-2.png',\n },\n ],\n },\n}\n\nuser_serializer = UserSerializer(data=data)\nuser_serializer.is_valid(raise_exception=True)\nuser = user_serializer.save()\n```\n\nThis serializer will automatically create all nested relations and we receive a\ncomplete instance with filled data.\n```python\nuser_serializer = UserSerializer(instance=user)\nprint(user_serializer.data)\n```\n\n```python\n{\n 'pk': 1,\n 'username': 'test',\n 'profile': {\n 'pk': 1,\n 'access_key': {\n 'pk': 1,\n 'key': 'key'\n },\n 'sites': [\n {\n 'pk': 1,\n 'url': 'http://google.com',\n },\n {\n 'pk': 2,\n 'url': 'http://yahoo.com',\n },\n ],\n 'avatars': [\n {\n 'pk': 1,\n 'image': 'image-1.png',\n },\n {\n 'pk': 2,\n 'image': 'image-2.png',\n },\n ],\n },\n}\n```\n\nIt is also possible to pass through values to nested serializers from the call\nto the base serializer's `save` method. These `kwargs` must be of type `dict`. E g:\n\n```python\n# user_serializer created with 'data' as above\nuser = user_serializer.save(\n profile={\n 'access_key': {'key': 'key2'},\n },\n)\nprint(user.profile.access_key.key)\n```\n\n```python\n'key2'\n```\n\nNote: The same value will be used for all nested instances like default value but with higher priority.\n\n\nTesting\n=======\nTo run unit tests, run:\n```bash\n# Setup the virtual environment\npython3 -m venv envname\nsource envname/bin/activate\n\npip install django\npip install django-rest-framework\npip install -r requirements.txt\n\n# Run tests\npy.test\n```\n\n\nKnown problems with solutions\n=============================\n\n\n##### Validation problem for nested serializers with unique fields on update\nWe have a special mixin `UniqueFieldsMixin` which solves this problem.\nThe mixin moves` UniqueValidator`'s from the validation stage to the save stage.\n\nIf you want more details, you can read related issues and articles:\nhttps://github.com/beda-software/drf-writable-nested/issues/1\nhttp://www.django-rest-framework.org/api-guide/validators/#updating-nested-serializers\n\n###### Example of usage:\n```python\nclass Child(models.Model):\n field = models.CharField(unique=True)\n\n\nclass Parent(models.Model):\n child = models.ForeignKey('Child')\n\n\nclass ChildSerializer(UniqueFieldsMixin, serializers.ModelSerializer):\n class Meta:\n model = Child\n\n\nclass ParentSerializer(NestedUpdateMixin, serializers.ModelSerializer):\n child = ChildSerializer()\n\n class Meta:\n model = Parent\n```\n\nNote: `UniqueFieldsMixin` must be applied only on serializer\nwhich has unique fields.\n\n###### Mixin ordering\nWhen you are using both mixins\n(`UniqueFieldsMixin` and `NestedCreateMixin` or `NestedUpdateMixin`)\nyou should put `UniqueFieldsMixin` ahead.\n\nFor example:\n```python\nclass ChildSerializer(UniqueFieldsMixin, NestedUpdateMixin,\n serializers.ModelSerializer):\n```\n\n##### Update problem for nested fields with form-data in `PATCH` and `PUT` methods\nThere is a special problem while we try to update any model object with nested fields\nwithin it via `PUT` or `PATCH` using form-data we can not update it. And it complains\nabout fields not provided. So far, we came to know that this is also a problem in DRF.\nBut we can follow a tricky way to solve it at least for now.\nSee the below solution about the problem\n\nIf you want more details, you can read related issues and articles:\nhttps://github.com/beda-software/drf-writable-nested/issues/106\nhttps://github.com/encode/django-rest-framework/issues/7262#issuecomment-737364846\n\n###### Example:\n```python\n\n# Models\nclass Voucher(models.Model):\n voucher_number = models.CharField(verbose_name=\"voucher number\", max_length=10, default='')\n image = models.ImageField(upload_to=\"vouchers/images/\", null=True, blank=True)\n\nclass VoucherRow(models.Model):\n voucher = models.ForeignKey(to='voucher.Voucher', on_delete=models.PROTECT, verbose_name='voucher',\n related_name='voucherrows', null=True)\n account = models.CharField(verbose_name=\"fortnox account number\", max_length=255)\n debit = models.DecimalField(verbose_name=\"amount\", decimal_places=2, default=0.00, max_digits=12)\n credit = models.DecimalField(verbose_name=\"amount\", decimal_places=2, default=0.00, max_digits=12)\n description = models.CharField(verbose_name=\"description\", max_length=100, null=True, blank=True)\n\n# Serializers for these models\nclass VoucherRowSerializer(WritableNestedModelSerializer):\n class Meta:\n model = VoucherRow\n fields = ('id', 'account', 'debit', 'credit', 'description',)\n\n\nclass VoucherSerializer(serializers.ModelSerializer):\n voucherrows = VoucherRowSerializer(many=True, required=False, read_only=True)\n class Meta:\n model = Voucher\n fields = ('id', 'participants', 'voucher_number', 'voucherrows', 'image')\n\n```\n\nNow if you want to update `Voucher` with `VoucherRow` and voucher image then you need to do it\nusing form-data via `PUT` or `PATCH` request where your `voucherrows` fields are nested field.\nWith the current implementation of the `drf-writable-nested` doesn't update it. Because it does\nnot support something like-\n\n```text\nvoucherrows[1].account=1120\nvoucherrows[1].debit=1000.00\nvoucherrows[1].credit=0.00\nvoucherrows[1].description='Debited from Bank Account' \nvoucherrows[2].account=1130\nvoucherrows[2].debit=0.00\nvoucherrows[2].credit=1000.00\nvoucherrows[2].description='Credited to Cash Account'\n\n```\nThis is not supported at least for now. So, we can achieve the result in a different way.\nInstead of sending the array fields separately in this way we can convert the whole fields\nalong with values in a `json` string like below and set it as value to the field `voucherrows`.\n\n```json\n\"[{\\\"account\\\": 1120, \\\"debit\\\": 1000.00, \\\"credit\\\": 0.00, \\\"description\\\": \\\"Debited from Bank Account\\\"}, {\\\"account\\\": 1130, \\\"debit\\\": 0.00, \\\"credit\\\": 1000.00, \\\"description\\\": \\\"Credited to Cash Account\\\"}]\"\n```\n\nNow it'll be actually sent as a single field value to the application for the field `voucherrows`.\nFrom your `views` you need to parse it like below before sending it to the serializer-\n\n```python\nclass VoucherViewSet(viewsets.ModelViewSet):\n serializer_class = VoucherSerializer\n queryset = serializer_class.Meta.model.objects.all().order_by('-created_at')\n \n def update(self, request, *args, **kwargs):\n request.data.update({'voucherrows': json.loads(request.data.pop('voucherrows', None))})\n return super().update(request, *args, **kwargs)\n```\nNow, you'll get the `voucherrows` field with data in the right format in your serializers.\nSimilar approach will be also applicable for generic views for django rest framework\n\nAuthors\n=======\n2014-2022, beda.software\n",
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