clojure - ( :gen-class) and fully qualified symbol

Question

我想知道为什么我需要包含 (:gen-class) 来访问从其他 ns 导入的函数而不完全限定它们。
例子:

(ns project.core
  (:gen-class))
(defn foo [] "foo")

(ns project.core-test
  (:gen-class)
  (:require [project.core :refer :all]))  
(foo) ;=> "foo"

(ns project.core)
(defn foo [] "foo")

(ns project.core-test
  (:require [project.core :refer :all]))  
(foo) ;=> ComplilerException java.lang.RuntimeException: Unable to resolve symbol: foo in this context
(project.core/foo) ;=> "foo"

我无法理解这个概念。
编辑:
我在 require 表单中有一个错字。不知道为什么 (:gen-class) 解决了这个问题，但现在该项目又可以正常工作了。

Answer 1

(:gen-class) ns中的条款表单用于提前编译 (AOT)。见 https://clojure.org/reference/compilation

您的设置中肯定还有其他问题。我的例子:

> d **/core*
-rw-rw-r-- 1 alan alan 98 Jan 13 16:15 src/fred/core.clj
-rw-rw-r-- 1 alan alan 47 Jan 13 16:15 src/tst/fred/core.clj

src/fred/core.clj
------------------------
(ns fred.core)

(defn foo [] (println "foo you"))

(defn -main []
  (println "main - enter")
  )


src/tst/fred/core.clj
----------------------
(ns tst.fred.core
  (:use fred.core ))

(foo)

> lein test
foo you 

我用 require 得到相同的结果版本:

(ns tst.fred.core
  (:require [fred.core :refer :all]))
(foo)

如果我将您的代码粘贴到 repl 中，它也有效:

~/tmp/fred > lein repl
Clojure 1.9.0

fred.core=> (ns project.core)
nil
project.core=> (defn foo [] "foo")
#'project.core/foo

project.core=> (ns project.core-test
          #_=>   (:require [project.core :refer :all]))  
nil
project.core-test=> (foo)
"foo"