Main如何在Clojure上工作

Question

I am with a problem with a clojure code, and I don't understand what is happen here.

Code:

(defn -main []
  (clean-bucket-if-limit)
  (do-something-1)
  (do-something-2)
  (do-something-3))


(defn clean-bucket-if-limit
  []
  (let [objects (get (s3/list-objects cred "deske") :objects)]
    (let [number (count objects)]
      (if (> 3 number)
        (map delete-file-s3 objects)
        (println "no limit")))))

(defn delete-file-s3
  [object]
  (let [key (get object :key)]
    (s3/delete-object cred "bucket-name" key)))

The problem is that when I execute clean-bucket-if-limit only (on REPL), everything works well, but when I use the main function not (files aren't deleted).

Answer 1

map is lazy . When you run (map delete xs) , you get back a lazy sequence immediately, and no work is actually done until you force the sequence by requesting elements from it. At the repl, the sequence is forced when it's printed to the screen. But when you run your program for real, -main returns void, and just discards the value it receives, causing nothing to ever be realized. You should use doseq or dorun or some other side-effectful sequence function if you want to iterate over a sequence for side effects, not just map .