Well, we’re into our first weeks of using cancan, and my earlier enthousiasm has been tempered somewhat. It turns out that Cancan, although being well-written, is an Opinionated plugin. It may have been intended only for very simple applications.
Let me explain. Authorization happens mostly at controller level. Cancan offers sweetened before_filter for this purpose. One being:
which will do some standard loading action for you (nesting is possible). It is implied that the model has the same name as your controller, let’s say a CommentsController will load and authorize based on the model Comment.
It’s made flexible to a certain extent, because you can specify another model, like
load_and_authorize_resource :class => Post
Besides that, you can decide to use your own before_filter to do your own custom loading of the model. If you don’t want to load, you can use
(without the load)
But for me we’re already in muddy waters, First off, I want authorization only, it’s unnecessary to load the instance variables for me, that’s not what I expect from this plugin. So I’ll stick with authorize_resource.
Secondly, we’re wanting to authorize a resource, not a model A resource, as in REST, should be disconnected from the model, that’s implied in the MVC pattern. The resource is what we expose to the outside world, whether as URL or in a more general API. Models are the developer’s business and nobody else’s. Linking both is awfully restrictive: usually, you’ll also have controllers that use several models, controllers that use a cache or set off background tasks etc.
This is possible with Cancan in a rather roundabout way, by using symbols when defining an authorization rule and making a before_filter.
This is why I decided to fork and add the required behaviour to the plugin. To quote what I added to the README:
If the resource is not linked to a model, you can use the authorize_resource filter with the :resource option. When the resource name is the controller name, use
(for instance CalendarsController will authorize on :calendar) When another name is required, a symbol can be used.
This may be enough for us to be able to work with it … we’ll see.