What is wrong with my simple Clojure gen-class script?

Question

I'm trying to learn how to use gen-class in Clojure. I've started with this simple script:

(gen-class :name MyClass :prefix MyClass-)

(defn MyClass-toString[this] "This Is My Class")

(println (MyClass.))

When I try to run it I get

    Exception in thread "main" java.lang.IllegalArgumentException: Unable to resolve classname: MyClass

What am I doing wrong?

kotarak · Accepted Answer · 2012-09-26 06:25:45Z

3

You need AOT compilation for gen-class.

answered Sep 26, 2012 at 6:25

kotarak

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1 Comment

Idan Arye Over a year ago

That did it! I put the class in a separate file and called compile on that file, and it works.

runexec · Accepted Answer · 2012-09-26 04:15:14Z

1

edit, Also, check that the main class name matches the one defined in the lein project file.

Usually you put in the (ns) header of the clj file.

(ns my.namespace
  (:gen-class))

Here's some examples

(gen-class
    :name "some.package.RefMap"
    :implements [java.util.Map]
    :state "state"
    :init "init"
    :constructors {[] []}
    :prefix "ref-map-")

edited Sep 26, 2012 at 4:15

answered Sep 26, 2012 at 3:55

runexec

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3 Comments

Idan Arye Over a year ago

I'm trying to run this as a script with clj, without Leiningen, in the default namespace. I couldn't get gen-class to work in a lein project, so I'm trying to run the simplest thing possible - one class, no namespace, no state, no inheritance. And this has nothing to do with the main class I'm trying to run - because the main class is not named MyClass and I'm not trying to run a class named MyClass(only to construct it) - and that's the class the Exception is talking about.

runexec Over a year ago

With or without lein, check that the class name matches the filename.clj. Just remember to replace '-' with '_'.

runexec Over a year ago

Also, please refer to the examples at clojuredocs.org/clojure_core/clojure.core/gen-class

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