How to call a gen-class method from clojure

Question

I'm Using gen-class to generate Java-classes from my Clojure code. In order to make gen-class work, I need to add an additional first parameter to all methods that will be added to the class (here called this).

(ns com.stackoverflow.clojure.testGenClass
  (:gen-class
     :name com.stackoverflow.clojure.TestGenClass
     :implements [com.stackoverflow.clojure.TestGenClassInterface]
     :prefix "java-"))

(def ^:private pre "START: ")

(defn java-addToString [this text post]
  (str pre text post))

After compilation, calling the method in a Java-context works fine.

(def var (com.stackoverflow.clojure.TestGenClass.))
(.addToString var "Aus Clojure heraus (Methode 1)." " :ENDE")
(. var addToString "Aus Clojure heraus (Methode 2)." " :ENDE")

But how can I start it directly from Clojure?

Thge following does not work, since the first parameter is missing.

(java-addToString "TexT" " :END")

Is it good practice to simply call the function with an empty first parameter?

(java-addToString "" "TexT" " :END")

Or should I add a function (e.g. addToString) that I use internally and call this function from the one that will be added as a method to the class-file?

noisesmith noisesmith · Accepted Answer · 2014-10-19T00:19:04

To want to treat the same code as a method on a generated class and as a function separate from said class seems a bit smelly to me (in the sense of code smell, something that indicates a problem somewhere in the design).

Perhaps addToString should be a static method?

Perhaps you should make an add-to-string function that can be used directly in clojure, and also called by the addToString method?

We'd need to know more about your larger design before we know the best answer, but I suspect it is one of those.

How to call a gen-class method from clojure

1 Answers