# drf-madprops [](https://travis-ci.com/yola/drf-madprops)
DRF library of helpers to operate on lists of resource properties as dicts
Written and used by the folks at Yola to support our [free website builder][1].
## Overview
It's a typical case for relational DBs when some table (e.g. User) is
extended via subordinate key-value table (e.g. UserPreference). This allows
to dynamically add/delete fields to User (stored in UserPreference).
Usually those property models have very simple structures, e.g:
```python
class UserPreference(models.Model):
id = models.AutoField()
user = models.ForeignKey(User, related_name='preferences')
name = models.CharField()
value = models.CharField)
```
But it's not very convenient to expose/operate on them via standard DRF
serializers. We'll get something like:
```json
[
{"id": "id1", "user": "user1", "name": "property1", "value": "value1"},
{"id": "id2", "user": "user1", "name": "property2", "value": "value2"}
...
]
```
This library contains two base classes for property's serializers (for cases
when properties are exposed as separate resource and as nested resource) which
allows to retrieve/operate on parent resource properties as dicts. For example,
instead of representation listed above, we'll get something like:
```json
{
"property1": "value1",
"property2": "value2",
...
}
```
## Usage
### Additional meta options
- `read_only_props`: list of property names, which values cannot be changed
via serializer.
- `json_props`: list of property names, which values are stored as JSON.
Serializer will `json.loads()` those values when converting to representation
and will `json.dumps()` them before saving.
### As a nested serializer
```python
from madprops.serializers import NestedPropertySerializer, PropertiesOwnerSerializer
class PreferenceSerializer(NestedPropertySerializer):
class Meta:
model = Preference
read_only_props = ('user_token', 'tutorial_email_sent')
json_props = ('packages',)
class UserSerializer(PropertiesOwnerSerializer):
preferences = PreferenceSerializer(many=True, required=False)
```
### As a serializer used for properties endpoint
```python
from madprops.serializers import PropertySerializer
class PreferenceSerializer(PropertySerializer):
class Meta:
model = Preference
read_only_props = ('user_token', 'tutorial_email_sent')
class PreferencePrivateViewSet(ModelViewSet):
serializer_class = PreferenceSerializer
paginate_by = None
```
## Testing
Run the tests with:
tox
Or install development requirements and run tests with:
pip install -r requirements.txt
pytest tests
[1]:https://www.yola.com/
