How to get the namespace of a var in Clojure?

Question

I am currently using the following which works - but it seems a bit of a cludge

(defn get-namespace
  [qualified-var]
  {:pre [(var? qualified-var)]}
  (the-ns
   (symbol
    (apply str (drop 2 (first (str/split (str qualified-var) #"/")))))))

ignoring the ugly string splitting (quick and dirty) is there a built in to do this?

do you want to write this as an aswer :D or should I just delete the question? — beoliver, Aug 11 '17 at 18:48
Seems useful q&a, either get @ez121sl to answer and accept or answer yourself and accept — Josh, Aug 11 '17 at 18:51
The question is fine. I'll write up the answer later or maybe someone else will do it in the mean time. — ez121sl, Aug 11 '17 at 18:51

score 3 · Accepted Answer · answered Aug 12 '17 at 01:24

The var's metadata contains a reference to its namespace under the :ns key. That would be the namespace in which the var is defined. The var's metadata can be accessed using the meta function. Putting it all together, we get (-> some-var meta :ns) and we can experiment a bit:

(def x "foo")
;; #'user/x
(-> #'x meta :ns)
;; #object[clojure.lang.Namespace 0x396bcdb0 "user"]
(-> #'clojure.core/map meta :ns)
;; #object[clojure.lang.Namespace 0x28412381 "clojure.core"]

A full example may look like this:

(defn var-namespace
  [qualified-var]
  {:pre [(var? qualified-var)]}
  (-> qualified-var meta :ns))

How to get the namespace of a var in Clojure?

1 Answers1