websauna.viewconfig 0.1

View override configuration pattern for Pyramid framework

• Features

• Development and tests

• Author

Features

websauna.viewconfig provides a class decorator @view_overrides which allows subclasses to partially override parent class view configuration. The primary use case is to have generic class views which you can subclass for more specific use cases. The pattern is very powerful when combined with Pyramid’s travesing contexts.

Example:

• There is a generic edit view for all of your models called GenericEdit

• But for a specific model, let’s say Car, you want to override parts of GenericEdit e.g. to include a widget to handle car colour selection. Other models, like House and Person, still use GenericEdit.

The code would be:

from websauna.viewconfig import view_overrides

class BaseModel:
     pass


class House(BaseModel):
     pass


class Car(BaseModel):
     pass


class GenericEdit:

    widgets = ["name", "price"]

    def __init__(self, context, request):
        self.context = context
        self.request = request

    @view_config(name="edit", context=BaseModel)
    def edit(self):
        # Lot's of edit logic code goes here which
        # we don't want to repeat....
        pass


@view_overrides(context=Car)
class CarEdit(GenericEdit):
    widgets = ["name", "price", "color", "year]


 class Root:
     """Pyramid's traversing root."""

     def __init__(self, request):
          pass

     def __getitem__(self, name):
         if is_car(name):
               return Car(name)
          else:
               return House(name):

Now one could traverse edit views like:

/my_house/edit
/my_car/edit

… and the latter would serve car-specific edit form.

The @view_overrides pattern can be also used with routing based views to override e.g route_name and renderer (the template of subclass view). For those examples, please see testing source code.

The implementation is based on venusian.lift() function with the overriding bits added in.

Development and tests

To run tests:

pip install -e ".[test]"
py.test websauna/viewconfig

To run coverage:

py.test --cov websauna.viewconfig --cov-report xml

All the testing on drone.io:

pip install -U pytest
pip install -e ".[test]"
py.test --cov websauna.viewconfig --cov-report xml
codecov --token="xxx"

Author

Mikko Ohtamaa (blog, Facebook, Twitter)