Akuna Component

Declarative component registration/lookup inspired by ZCA component architecture with a simple api allowing for great decoupling between component clients and components.

Best explained as an example:

>>> class Bike(object): 
...     pass
...
>>> class MountainBike(Bike): 
...     pass
...
>>> class RoadBike(Bike): 
...     pass
...

>>> class Request(object): 
...     pass
...

>>> class View(object):
...     def render_view(self):
...         pass
...

Our View components:

>>> from akuna.component import register_component
...

Some generic BikeView component (extending View):

>>> @register_component(context=('Bike', 'Request'))
... class GenericBikeView(View):
...     def __init__(self, bike, request):
...         pass 
...         

A more specific MountainBikeView component:

>>> @register_component(context=('MountainBike', 'Request'))
... class MountainBikeView(View):
...     def __init__(self, mountain_bike, request): 
...         pass
...

Some example context objects to test our component setup:

>>> road_bike = RoadBike()
>>> mountain_bike = MountainBike()
>>> request = Request()

Finally component lookup to find most applicable component for a given context:

>>> from akuna.component import query_component 
>>>
>>> query_component('View', context=(mountain_bike, request))
<class '__main__.MountainBikeView'>

Similar query but for RoadBike, Request context. Note the Generic View component being returned as we don't have a specific RoadBike view component (RoadBike is a Bike and we have registered a generic Bike view):

>>> query_component('View', context=(road_bike, request))
<class '__main__.GenericBikeView'>

Components could also be registered using a component name, and without context. Or providing is_a argument to override type. This could be useful when registering functions as components. Usually we would search components by type (eg. View, Factory):

>>> @register_component(is_a='Factory', name='mountainbike')
... def mountainbike_factory():
...     pass
...

Components could be objects:

>>> class Factory(object): 
...     pass
...

>>> class MyFactory(Factory): 
...     pass
...

>>> my_factory = MyFactory()
>>> register_component(my_factory)
...

Factory component search will return MyFactory instance:

>>> query_component('Factory')      #doctest: +ELLIPSIS
<__main__.MyFactory object at ...>

More specific search by component name:

>>> query_component('Factory', name='mountainbike')     #doctest: +ELLIPSIS   
<function mountainbike_factory ...>

You could instantiate a component when looking it up. Context objects will be passed to the component as constructor args:

>>> query_component('View', context=(road_bike, request), instantiate=True)   #doctest: +ELLIPSIS
<__main__.GenericBikeView object at ...>

If component not found, query_component will return None. get_component could be used in exactly the same way as query_component but error will be thrown if component not found:

>>> from akuna.component import get_component
>>> get_component('Factory', name='blah')       #doctest: +IGNORE_EXCEPTION_DETAIL
Traceback (most recent call last):
ComponentDoesNotExist:...

Django Update View form hook example

This simple example extends Django's Update View to add a form class component hook. Form classes registered by content model name of the object being updated.

from django.views.generic.edit import UpdateView

class UpdateViewWithFormHook(UpdateView):
    def get_form_class(self):
        obj_to_upd = self.get_object()
        content_model_name = obj_to_upd._meta.model_name
        if not self.form_class:
            try:
                # our form hook
                self.form_class = query_component('Form', name=content_model_name)
            except ComponentDoesNotExist:
                # fallback to some generic form 
                self.form_class = modelform_factory(obj_to_upd.__class__)

        return super(UpdateViewWithFormHook, self).get_form_class()

Just register a few forms which will plug into the above view based on the model_name of the object being updated.

@register_component(name='customer')
class CustomerForm(forms.Form):
    pass  

@register_component(name='cartitem')
class CartItemForm(forms.Form):
    pass