Problem with gen-class, cannot get basic stuff to work

[Benny_Mildh]

Hello!

In my top level project folder, “Searchbar” I have a deps.edn file:

{:paths ["src" "test" "classes"]
 :deps {org.openjfx/javafx-controls {:mvn/version "15-ea+2"}
        org.openjfx/javafx-base {:mvn/version "15-ea+2"}
        org.openjfx/javafx-graphics {:mvn/version "15-ea+2"}
        org.openjfx/javafx-fxml {:mvn/version "15-ea+2"}}}

In my src/searchbar/core.clj file:

(ns searchbar.core)

(import (javafx.application.Application)
        (javafx.fxml.FXMLLoader)
        (javafx.stage.Stage)
        (javafx.scene.Scene))

(gen-class :name "searchbar.JfxGUI" :extends [javafx.application.Application])

(defn -start [stage]
  (println "Inside the start function"))
(defn -main [& args]
  (println "Inside main")
  (launch))

When I try to run this with:

clojure -m searchbar.core

Syntax error macroexpanding clojure.core/import at (searchbar/core.clj:3:1).
javafx.application.Application - failed: #{(quote quote)} at: [:class :quoted-spec :quote] spec: :clojure.core.specs.alp
ha/quotable-import-list
() - failed: Insufficient input at: [:package-list :spec :classes] spec: :clojure.core.specs.alpha/package-list
javafx.application.Application - failed: #{(quote quote)} at: [:package-list :quoted-spec :quote] spec: :clojure.core.sp
ecs.alpha/quotable-import-list
(javafx.application.Application) - failed: simple-symbol? at: [:class :spec] spec: :clojure.core.specs.alpha/quotable-im
port-list

Could anyone shed some light over what I’m doing wrong? It feels like I’m missing syntax but I’m not sure.

[mdiin]

One problem is that you need to separate the classes from their packages when using import: (import (java.util Date)), not (import (java.util.Date)).

See http://clojuredocs.org/clojure.core/import for more examples.

In general, while you can call import, require and gen-class as functions, it is usually a good idea to include them in the namespace declaration: (ns goo.bar (:import (java.util Date)) (:gen-class)). Note that they are keywords in this case.

[Benny_Mildh]

Ah, I seem to have missed that. Reading the doc there is indeed a space between package and class.

But in the first example below the description:

(import java.util.Date)

Soo… confused.

Thank you.

Edit: The reason I’m doing it explicitly is because I’m just learning the basics. It feel intuitive easier to call import, require, gen-class. Like you mention, It seems the standard way is to use keywords from what I’ve seen at other sources, but I have not quite yet grasped the fundamentals yet (obviously)(like, I thought you only used keywords with maps {}, but here it is in list forms. Anyway. Much to learn.

[didibus]

Ya, this is one of the quirks of Clojure, the require and import clauses have a bit of an inconsistent non-intuitive syntax.

import can take one or more “import symbol” or “import list” where an import symbol is a fully qualified package.class like java.util.Date. Or where an import list is a list like (package class1 class2 class3).

[Benny_Mildh]

Thank you for clearing that up.

[Phill]

The stand-alone import takes a literal list (you must quote it), while the ns form takes an embedded :import clause without a quote. The error message in the original post was telling you that the import expected a literal list.

You can write either

(ns searchbar.core
  (:import (javafx.application Application)
     ;; etc        
))

or

(ns searchbar.core)
(import '(javafx.application Application)
     ;; etc        
)

[Benny_Mildh]

Ah, yes, thank you. It starts to get clearer now.

One thing I did not realize, is that you have to compile the code first. I’m using emacs/cider, so when I just evaluate my buffer, I will get a ClassNotFound on searchbar.core. Now, If go the repl, call the compile function, change into the my namespace, voila, It works. To be fair, that is in the docs somewhere, just a lot of examples on the interweb where it is simply not mentioned. You kinda get spoiled in the beginning learning clojure, just living in the repl, even if you have a file/buffer, you just send it to the repl. As soon as you go into interop, things change.