Got it. You cannot invoke (import) (or (ns)) from within the function
definition. The function is already being evaluated, and it's "too
late".
This works fine for me:
(do
(import '(javax.swing JOptionPane))
((fn []
(println "Hello World")
(println (+ 2 2))
(JOptionPane/showMessageDialog
nil "Hello from the text panel" "Greeting"
JOptionPane/INFORMATION_MESSAGE))))
So be aware that then some namespace will be changed by the call to
import (side effect on *ns*).
I would suggest either you create a temporary namespace for the code
to execute, either as Sean suggested, you write the call to
JOptionPane static methods and fields fully qualified:
(javax.swing.JOptionPane/showMessageDialog ...)
HTH,
--
Laurent
2010/9/10 Paul D. Fernhout <[email protected]>:
> I'm just trying out Clojure a bit, so this may be an obvious simple thing
> I'm misunderstanding.
>
> This code in the test file below allows editing a Clojure function that is
> updated when an "Update Code" button is pressed, with the new value
> connected to a GUI button "Click Me!" as a proxy ActionListener.
>
> It starts with a default function that has not been dynamically loaded from
> a string that pops up a JOptionPane that displays the text in the text pane.
>
> Evaluating simple code like "(fn [] (println \"Hello World\"))"
> with no import dependencies works.
>
> What am I doing wrong to not have the evaluated code have access to
> JOptionPane?
>
> I get:
>
> user=> Exception in thread "AWT-EventQueue-0" java.lang.Exception: No such
> namespace: JOptionPane (NO_SOURCE_FILE:6)
>
> when I try the "Update Code" button.
>
> The initial text includes an import statement.
>
> What do I misunderstand that the import does not seem to work?
>
> Anyway, I'm new to Clojure, so I don't really get the import or ns command
> that well yet. Any suggestions would be appreciated. Feel free to treat this
> code example as if it were in the public domain.
>
> =========== guitest2.clj
>
> (ns org.pointrel.guitest2
> ;(:require )
> ;(:use )
> ;(:import )
> )
>
> (import
> '(javax.swing JFrame JPanel JButton JOptionPane JTextPane)
> '(java.awt.event ActionListener))
>
> (defn hookupActionPerformed [receiver function]
> (println "updating hook" receiver function)
> (let [act (proxy [ActionListener] [] (actionPerformed [event] (function)))]
> (.addActionListener receiver act)
> )
> )
>
> (def initial-text "(fn []
> (println \"Hello World\")
> (println (+ 2 2))
> ;(ns org.pointrel.guitest2)
> (import '(javax.swing JOptionPane))
> (JOptionPane/showMessageDialog
> nil \"Hello from the text panel\" \"Greeting\"
> JOptionPane/INFORMATION_MESSAGE)
> )"
> )
>
> (defn window []
> (def frame (JFrame. "Hello Frame"))
>
> (def panel (JPanel.))
> (.setContentPane frame panel)
>
> (def test-button (JButton. "Click Me!"))
> (.add panel test-button)
>
> (def update-button (JButton. "Update code"))
> (.add panel update-button)
>
> (def text (JTextPane.))
> (.setText text initial-text)
> (.add panel text)
>
> (defn say-hello []
> (let [text-contents (.getText text)]
> (JOptionPane/showMessageDialog
> nil text-contents "Greeting"
> JOptionPane/INFORMATION_MESSAGE)))
>
> (hookupActionPerformed test-button say-hello)
>
> (defn update-code []
> (let [text-contents (.getText text)
> discard (printf text-contents)
> user-function (load-string text-contents)]
> (println "update-code")
> (.removeActionListener test-button (aget (.getListeners test-button
> ActionListener) 0))
> (hookupActionPerformed test-button user-function)
> ))
>
> (hookupActionPerformed update-button update-code)
>
> (.setSize frame 200 200)
> (.setVisible frame true)
> )
>
> (window)
>
> ; (eval (read-string "(println \"Hello World\")"))
> ; (load-string "(fn [] (println \"Hello World\"))")
> ; (eval ((fn [] (println "Hello World2"))))
>
> ===========
>
> There's probably stylistic issue, too. :-)
>
> By the way, the println calls don't seem to show up in NetBeans 6.9.1 with
> Enclojure after the window opens, and when I try to use code that generates
> an error I get "Repl is disconnected" that I don't know how to recover from
> without restarting NetBeans, so I am testing this with:
>
> $ java -cp jline-0.9.94.jar:clojure.jar jline.ConsoleRunner clojure.main
> Clojure 1.2.0
> user=> (load-file "guitest2.clj")
>
> --Paul Fernhout
> http://www.pdfernhout.net/
> ====
> The biggest challenge of the 21st century is the irony of technologies of
> abundance in the hands of those thinking in terms of scarcity.
>
> --
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