How to get a clojure handle on a Java static method, similar to _memfn_ for a Java instance method?

Question

To get a handle on a Java instance method which we can invoke later on, we can call the memfn function:

user=> (def g (memfn Integer/toString))
#'user/g

user=> (g 789)
"789"

This doesn't work for Java static methods:

user=> (def g (memfn Integer/toHexString))
#'user/g

user=> (g 789)
IllegalArgumentException No matching method found: toHexString for class java.lang.Long  clojure.lang.Reflector.invokeMatchingMethod (Reflector.java:52)

user=> (g)
ArityException Wrong number of args (0) passed to: user$g  clojure.lang.AFn.throwArity (AFn.java:437)

How can we get a handle to a Java static method, so we can invoke it later on?

The anonymous function literal, #(.foo ...), is generally preferred over memfn, so too would it be for static methods. — Alex Taggart
– Alex Taggart, Commented Dec 24, 2011 at 7:33

amalloy · Accepted Answer · 2011-12-24 06:35:40Z

7

(defn g [x] (Integer/toHexString x))...? If you want, you can wrap that up in a macro, but there's not much left to do:

(defmacro static-fn [f] `(fn [x#] (~f x#)))
(def g (static-fn Integer/toHexString))

answered Dec 24, 2011 at 6:35

amalloy

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1 Comment

Vorg van Geir Over a year ago

Thanks, this gave me a nudge towards the much harder problem I had which required two levels of back-quoting and escaping.

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