I believe maps containing functions are generally looked down upon.
Multimethods are probably the way to go. Can't you tag your request map with
a type?
On Thu, Sep 17, 2009 at 7:50 AM, Philipp Meier <phme...@gmail.com> wrote:
>
> Hi,
>
> I'm building a REST server library on top of compojure loosely modeled
> after the ideas of erlangs webmachine. The idea is to describe a
> resource using a couple of function which server as decision makers
> for the different stages of HTTP request processing. There will be a
> function to determine if the request method is allowed, if the request
> is authorized, a method to produce an ETAG or to process the request
> body in case of a POST request. Something like
>
> (defn valid-method? [request] (= (get-method request) :get)
> (defn generate-etag [request] (make-hash-md5 (get-path request)))
> (defn process-post [request] (str "The body was" (get-body request))
>
> The question is: how can on group the methods together for different
> resources and to enable fall back do default implementation of the
> methods (e.g. generate an etag by sha-ing the response body)?
>
> Two solutions come to my mind: multimethods and maps of methods.
>
> For multimethods id declare a type :rest-ressource which methods will
> serve as a default implementation and that could be overridden by each
> sub type resource.
>
> By maps of methods I mean something like
>
> (def rest-default-impl {
> :valid-method? (fn [request] (contains [:head :get] (get-method
> request)))
> # ...
> })
>
> (defn make-rest [method-map]
> (merge rest-default-impl method-map))
>
> (def test-resource make-rest({ :valid-method? (fn [request] (= (get-
> method request) :get))
> :body { :text/html (fn
> [request] "Hello, world.") }}))
>
>
>
> Which way would you prefer? What are to advantaces and drawbacks of
> each? The method-map approach seams more fp to me, but, I think that's
> like how multimethods are impemented, aren't they?
>
> -billy.
> >
>
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