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Message from discussion ClassCastException clojure.lang.Var$Unbound Help
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Dave Ray  
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 More options Apr 30 2012, 9:30 pm
From: Dave Ray <dave...@gmail.com>
Date: Mon, 30 Apr 2012 21:30:47 -0400
Local: Mon, Apr 30 2012 9:30 pm
Subject: Re: ClassCastException clojure.lang.Var$Unbound Help
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I think what you actually want is:

(defn get-id []
  (session/get :uid))

in your code, you're trying to call #'session/get directly and bind it
to get-id. Of course, the problem with this is that #'session/get
expects to be called in the context of a request which is where your
Unbound var exception is coming from.

Hope this helps,

Dave

On Mon, Apr 30, 2012 at 11:39 AM, Travis Smith <tra...@legomaster.net> wrote:
> What does 'java.lang.ClassCastException: clojure.lang.Var$Unbound cannot be
> cast to clojure.lang.IDeref' mean. I'm getting this a lot and I want to
> understand it better, make it easier for me to avoid this. Most of the time
> I just end up adjusting my def/defn's around until it works. This is hardly
> optimal.

> (this is all on clojure 1.3.0)

> An example...

> (ns app-admin.models.current-user
>   (:require [noir.session :as session]
>             [app-admin.models.users :as users]))

> (def get-id
>   (session/get :uid))

> (defn set-user! [user]
>   (session/put! :uid {:_id user}))

> Give me an exception for get-id

> ClassCastException clojure.lang.Var$Unbound cannot be cast to
> clojure.lang.IDeref  clojure.core/deref (core.clj:2078)

> So set-user! binds correctly, but get-id doesn't seem to...

> => (get-id)
> llegalStateException Attempting to call unbound fn:
> #'app-admin.models.current-user/get-id  clojure.lang.Var$Unbound.throwArity
> (Var.java:43)

> Then I check it...

> => (meta #'get-id)
> {:ns #<Namespace app-admin.models.current-user>, :name get-id}

> So it's there, the fn is bound; I'm not exactly sure what's going on and nor
> what I'm missing about how this works to help me avoid problems like this in
> future. Just guessing and tweaking has gotten me so far, but that's not
> sustainable.

> Thanks!

> -Travis

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