>Command line arguments that are not strings need to be converted
> prior to use by your main function.
That makes sense, I need to cast it to a symbol, yes? I have a problem with
that though. At the REPL I tried something like this:
(def hey (resolve (symbol what-to-do)))
which worked great at the REPL, but in my code I get "nil" returned from
resolve. If I do this:
(defn -main [& args]
(let [port (Integer/parseInt (first args))
service (resolve (symbol (second args)))]
(println "Server is starting")
(println "port: " port)
(println (second args))
(println (symbol (second args)))
(println "service: " service)
(run-server port service)))
And call it like this:
java -jar who-is-logged-in-1.0.0-SNAPSHOT-standalone.jar 3456
"who-is-here-now"
Everything looks correct till the final line when I get "nil":
Server is starting
port: 3456
who-is-here-now
who-is-here-now
service: nil
On Tuesday, August 28, 2012 6:53:24 AM UTC-4, Jon_Boone wrote:
>
> Command line arguments that are not strings need to be converted prior to
> use by your main function.
>
> Look at the code for the port number and do the same for the service.
>
> --jon
>
>
> On Aug 28, 2012, at 2:42, larry google groups
> <[email protected]<javascript:>>
> wrote:
>
>
> So, this started when I read Keith Swallow's article on a simple web
> server:
>
> http://keithcelt.com/a-simple-web-server-in-clojure
>
> I took his code and ran "lein new" to create a new project and I copy and
> pasted his code to core.clj and made some minor adjustments, adding
> gen-class and main so I could run this from the command line. My main
> function looked like this:
>
> (defn -main [& args]
> (let [port (Integer/parseInt (first args))]
> (println "Server is starting")
> (run-server port echo)))
>
> Which called his function:
>
> (defn run-server [port service]
> (let [server-socket (create-socket port)]
> (while (not (. server-socket isClosed))
>
> (listen-and-respond server-socket service))))
>
> I compiled that and ran "lein uberjar" and then ran it from the command
> line and it worked great.
>
> Then, to make it slightly more flexible, I wanted to hand in the name of
> the service from the command line. So I made a minor change:
>
>
> (defn run-server [port what-to-do]
> (let [server-socket (ServerSocket. "localhost" port)]
> (while (not (. server-socket isClosed))
> (listen-and-respond server-socket what-to-do))))
>
> (defn -main [& args]
> (let [port (Integer/parseInt (first args))
> service (second args)]
> (println "Server is starting")
> (println "port: " port)
> (println "service: " service)
> (run-server port service)))
>
> I compiled this and ran it. And now this line:
>
> (defn run-server [port what-to-do]
>
> Gets this error:
>
> Exception in thread "main" java.lang.ClassCastException: java.lang.String
> cannot be cast to java.lang.Number
> at who_is_logged_in.core$run_server.invoke(core.clj:27)
>
> I'm calling it from the command line with:
>
> java -jar who-is-logged-in-1.0.0-SNAPSHOT-standalone.jar 3456
> who-is-here-now
>
> I also tried putting the service name in quotes:
>
> java -jar who-is-logged-in-1.0.0-SNAPSHOT-standalone.jar 3456
> "who-is-here-now"
>
> Can anyone tell me what is wrong? Why does Clojure think I'm trying to
> cast "who-is-here-now" to a number?
>
>
>
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