### Project Testing Setup and Execution

Source: https://github.com/beda-software/drf-writable-nested/blob/master/README.md

Provides commands to set up a Python virtual environment, install dependencies like Django and DRF, and run unit tests using py.test.

```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
```

--------------------------------

### Install drf-writable-nested

Source: https://github.com/beda-software/drf-writable-nested/blob/master/README.md

Installs the drf-writable-nested package using pip. Ensure you have Python and pip configured.

```bash
pip install drf-writable-nested
```

--------------------------------

### Prepare Nested Data for Creation

Source: https://github.com/beda-software/drf-writable-nested/blob/master/README.md

An example Python dictionary representing the data structure for creating nested models. This data is passed to the main serializer for processing.

```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',
            },
        ],
    },
}
```

--------------------------------

### Example Serialized Output

Source: https://github.com/beda-software/drf-writable-nested/blob/master/README.md

The resulting serialized data structure after saving the nested objects. It includes primary keys for all created nested instances.

```json
{
    "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"
            }
        ]
    }
}
```

--------------------------------

### Save Nested Data Example

Source: https://github.com/beda-software/drf-writable-nested/blob/master/README.md

Demonstrates saving data with nested serializer structures, including a profile with an access key. Shows how to access the saved nested data.

```python
user_serializer = UserSerializer(data=request.data)
user = user_serializer.save(
    profile={
        'access_key': {'key': 'key2'},
    },
)
print(user.profile.access_key.key)
```

--------------------------------

### JSON String Format for Nested Array Data

Source: https://github.com/beda-software/drf-writable-nested/blob/master/README.md

Example of how to format nested array data (e.g., for 'voucherrows') as a JSON string to be sent in a PUT or PATCH request when direct nested array parsing is not supported.

```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"}]
```

--------------------------------

### Serialize and Save Nested Data

Source: https://github.com/beda-software/drf-writable-nested/blob/master/README.md

Demonstrates instantiating a serializer with data, validating it, and saving the nested objects. The `save()` method handles the creation of all related nested instances.

```python
user_serializer = UserSerializer(data=data)
user_serializer.is_valid(raise_exception=True)
user = user_serializer.save()
```

--------------------------------

### Mixin Ordering for UniqueFieldsMixin

Source: https://github.com/beda-software/drf-writable-nested/blob/master/README.md

Shows the correct order when applying UniqueFieldsMixin with other mixins like NestedUpdateMixin or NestedCreateMixin to ensure proper functionality.

```python
class ChildSerializer(UniqueFieldsMixin, NestedUpdateMixin, serializers.ModelSerializer):
    # ... serializer definition
```

--------------------------------

### Retrieve Serialized Nested Data

Source: https://github.com/beda-software/drf-writable-nested/blob/master/README.md

Shows how to serialize an existing instance to retrieve its data, including all nested related fields. This is useful for displaying or verifying the created data.

```python
user_serializer = UserSerializer(instance=user)
print(user_serializer.data)
```

--------------------------------

### VoucherRow Serializer

Source: https://github.com/beda-software/drf-writable-nested/blob/master/README.md

Defines a WritableNestedModelSerializer for the VoucherRow model, specifying fields for id, account, debit, credit, and description.

```python
class VoucherRowSerializer(WritableNestedModelSerializer):
    class Meta:
        model = VoucherRow
        fields = ('id', 'account', 'debit', 'credit', 'description',)
```

--------------------------------

### Create Writable Nested Serializers

Source: https://github.com/beda-software/drf-writable-nested/blob/master/README.md

Defines DRF serializers using WritableNestedModelSerializer to handle nested model data. It specifies how related models (e.g., sites, avatars, access_key, profile) are nested within the main serializer.

```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',)
```

--------------------------------

### Voucher Serializer with Nested Rows

Source: https://github.com/beda-software/drf-writable-nested/blob/master/README.md

Defines a ModelSerializer for the Voucher model, including a nested, read-only VoucherRowSerializer for the 'voucherrows' field.

```python
class VoucherSerializer(serializers.ModelSerializer):
    voucherrows = VoucherRowSerializer(many=True, required=False, read_only=True)
    class Meta:
        model = Voucher
        fields = ('id', 'participants', 'voucher_number', 'voucherrows', 'image')
```

--------------------------------

### Update Handling for Nested Arrays in DRF View

Source: https://github.com/beda-software/drf-writable-nested/blob/master/README.md

Demonstrates a workaround in a Django REST Framework ModelViewSet to handle updates for nested array fields (like 'voucherrows') by parsing a JSON string from the request data before passing it to the serializer.

```python
import json
from rest_framework import viewsets

class VoucherViewSet(viewsets.ModelViewSet):
    serializer_class = VoucherSerializer
    queryset = serializer_class.Meta.model.objects.all().order_by('-created_at')
    
    def update(self, request, *args, **kwargs):
        # Parse 'voucherrows' from JSON string in request data
        request.data.update({'voucherrows': json.loads(request.data.pop('voucherrows', None))})
        return super().update(request, *args, **kwargs)
```

--------------------------------

### UniqueFieldsMixin for Nested Serializers

Source: https://github.com/beda-software/drf-writable-nested/blob/master/README.md

Illustrates how to use UniqueFieldsMixin with Django REST Framework serializers to handle unique field validation during the save stage for nested models.

```python
from rest_framework import serializers
from drf_writable_nested.mixins import UniqueFieldsMixin, NestedUpdateMixin

# Assume models Child and Parent are defined elsewhere

class ChildSerializer(UniqueFieldsMixin, serializers.ModelSerializer):
    class Meta:
        model = Child

class ParentSerializer(NestedUpdateMixin, serializers.ModelSerializer):
    child = ChildSerializer()

    class Meta:
        model = Parent
```

--------------------------------

### Define Django Models for Nested Serialization

Source: https://github.com/beda-software/drf-writable-nested/blob/master/README.md

Defines Django models including OneToOne, ForeignKey, and ManyToMany relationships. These models serve as the data structure for nested serialization.

```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)
```

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