[GMG-Devel] [proposal] Class-based views

[Joar Wandborg]

This is my proposal for the new view structure, feedback welcome.

These are changes that would be implemented to help in the development of
the MediaGoblin API.

Currently we have method-based views

- Views are methods with at least one parameter (request) that holds request
  information and additional instantiated objects and methods such as `db`,
  `user`, `staticdirect`, `session`. 
- View methods are decorated to, for example:
  - Force login on the current page.
  - Enable pagination
  - Fetch a model to a view based on request data

What we would need is

- Separate common logic from rendering logic
- Have multiple rendering methods (`as_json()`, `as_html()`)
- Provide classes for, for example pagination and fetching a model based on
  request data ('mixin's?)

    class MediaView(View, MediaEntryMixin):
        def setup(self):
            pass
        
        def as_json(self):
            import simplejson
            simplejson.dumps(self.media.public_data())

        def as_html(self):
            return render_to_response(
                request,
                get_media_manager(media.media_type)['display_template'],
                {'media': self.media,
                 'comments': comments,
                 'pagination': pagination
                 ...}


    class MediaEntryMixin(object):
        @property
        def media(self):
            if self._media:
                return self._media
            else:
                self._media = self.request.db.MediaEntry.find_one(
                    ...)
    

    class View(object):
        def __init__(self, request):
            self.request = request

        def __call__(self, request):
            self.setup()

            if wants_json:
                return self.as_json()
            else:
                return self.as_html()