On 12 May 2011 00:04, Shree Mulay <[email protected]> wrote:
> From this code, I can't figure out where you "instantiate" the session
> var, store to it, and read back from it? I know there's not
> instantiation in clojure(???). I hope your able to get what I'm having
> trouble figuring out.
The session is read from a :session key on the request map, and
written using a :session key on the response map.
For example, this route returns the value of the session key :x
(GET "/get" {session :session}
(str "x = " (:x session)))
It's equivalent to the Sinatra route:
get "/get" do
"x = #{session[:x]}"
end
The main difference is that the session has to be bound explicitly. We
don't just get a magic session map hanging around in the background.
Writing a session is a little trickier:
(GET "/set" [x :as {session :session}]
{:session (assoc session :x x)
:body (str "You set x = " x)})
The equivalent Sinatra route is:
get "/set" do |x|
session[:x] = x
"You set x = #{x}"
end
Ring sessions are a little unwieldy because you write by changing the
response, rather than calling a side-effectful function. Sandbar takes
a slightly different approach that looks more like the Sinatra code:
(GET "/get" []
(str "x = " (session-get :x)))
(GET "/set" [x]
(session-put! :x x)
(str "You set x = " x))
Sandbar is a little cleaner for simple things, but Ring sessions have
the advantage of working well with middleware. Idiomatic Ring tends to
use a lot of middleware, far more than one might use in Rack (for
instance).
- James
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