在 Clojure 中：在函数内部使用 let 执行 Java 调用时出错，但在 REPL 中则不然

发布于 2024-09-08 19:31:57 字数 2562 浏览 5 评论 0原文

我有以下代码：

(defn post
  [title content timestamp]
    (let [[innholdet tajm]
       [(str "<html>
              <head>
              <title>" title " :: " blog_title "</title></head>
              <body><h1>" title "</h1>
              <br/>" content "<br/><i>posted " (Date. timestamp) "</i>
              <br/><a href=\"" (str blog_url) "\">[main]</a> | 
              <a href=\"" (str blog_url) "/" timestamp ".html\">[permalink]</a>
              </body></html>") (str timestamp".html")]]
                 (spit tajm innholdet)
   )
 )

我有另一个函数，它将标题、内容和 UNIX 时间戳传递给上面的函数“post”。 blog_title 和 blog_url 是在代码顶部定义的 var。我已经对 HTML 进行了美观排序，但在“真实代码”中情况并非如此。我也在做

(import 'java.util.Date)
(use 'clojure.string)

如果我尝试执行代码，我会收到错误

java.lang.IllegalArgumentException

如果我删除 (Date.timestamp) 代码可以完美执行，但我需要具有 (Date.) 函数。

现在，如果在 REPL 中我这样做

(import 'java.util.Date)

然后定义一个带有时间戳的 var

(def timestamp 1278854531000) ;; Just for pushing a var into (Date.) than just the number

然后我只需将 (let) 复制到 REPL 中并调整原始代码中的变量以表示不同的函数名称而不是值（因为这是REPL 和原始代码中的变量、函数和值不存在），就像这样：

(let [[innholdet tajm] 
  [(str "<html>
         <head>
         <title>" (str "title") " :: " (str "blog_title") "</title>
         </head>
         <body><h1>" (str "title") "</h1><br/>" (str "content") "<br/>
         <i>posted " (Date. timestamp) "</i><br/>
         <a href=\"" (str "blog_url") "\">[main]</a> | 
         <a href=\"" (str "blog_url") "/" (str "1278854531000") ".html\">[permalink]</a></body></html>") 
         (str "1278854531000.html")]] 
           (println innholdet tajm))

现在 REPL 给了我：

<html>
<head>
<title>title :: blog_title</title>
</head>
<body>
<h1>title</h1><br/>content<br/>
<i>posted Sun Jul 11 15:22:11 CEST 2010</i><br/>
<a href="blog_url">[main]</a> | 
<a href="blog_url/1278854531000.html">[permalink]</a>
</body></html> 
1278854531000.html
nil

再次，所有内容都已转移，以便在 REPL 中更容易阅读出现在一大串中。

这里的问题是，我可以在 REPL 中执行代码并获取 (Date.timestamp) 的值并且一切正常，但是当我在程序中的函数内部执行它时，我收到上述错误。如果有人能告诉我我在这里缺少什么，我将不胜感激。

原文

I have the following code:

(defn post
  [title content timestamp]
    (let [[innholdet tajm]
       [(str "<html>
              <head>
              <title>" title " :: " blog_title "</title></head>
              <body><h1>" title "</h1>
              <br/>" content "<br/><i>posted " (Date. timestamp) "</i>
              <br/><a href=\"" (str blog_url) "\">[main]</a> | 
              <a href=\"" (str blog_url) "/" timestamp ".html\">[permalink]</a>
              </body></html>") (str timestamp".html")]]
                 (spit tajm innholdet)
   )
 )

I have another function that passes a title, the content and a UNIX timestamp to the function "post" above. blog_title and blog_url is var defined at the top of the code. I have sorted the HTML for aesthetics, in the "real code" this is no the case. I am also doing

(import 'java.util.Date)
(use 'clojure.string)

If I try to execute the code I get an error

java.lang.IllegalArgumentException

If I remove (Date. timestamp) the code executes perfectly, but I need to have that (Date.) function.

Now, if in REPL I do

(import 'java.util.Date)

Then define a var with a timestamp

(def timestamp 1278854531000) ;; Just for pushing a var into (Date.) than just the number

And then I just copy the (let) into REPL and adjust the vars in the original code to rather just represent the different function names instead of the values (since this is the REPL and the vars, functions and values that are in the original code doesn't exist), to be like this:

(let [[innholdet tajm] 
  [(str "<html>
         <head>
         <title>" (str "title") " :: " (str "blog_title") "</title>
         </head>
         <body><h1>" (str "title") "</h1><br/>" (str "content") "<br/>
         <i>posted " (Date. timestamp) "</i><br/>
         <a href=\"" (str "blog_url") "\">[main]</a> | 
         <a href=\"" (str "blog_url") "/" (str "1278854531000") ".html\">[permalink]</a></body></html>") 
         (str "1278854531000.html")]] 
           (println innholdet tajm))

Now the REPL gives me:

<html>
<head>
<title>title :: blog_title</title>
</head>
<body>
<h1>title</h1><br/>content<br/>
<i>posted Sun Jul 11 15:22:11 CEST 2010</i><br/>
<a href="blog_url">[main]</a> | 
<a href="blog_url/1278854531000.html">[permalink]</a>
</body></html> 
1278854531000.html
nil

Again, everything has been shifted so that it would be more friendly to read, in REPL everything comes out in one large string.

The problem here is that I can execute the code in REPL and get the value of (Date. timestamp) and everything works out, but when I execute it inside of a function in my program I get the above mentioned error. Would appreciate if anyone could tell me what I am missing here.

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疯狂的代价 2024-09-15 19:31:57

只需要进行一个小更改即可：

(defn post
  [title content timestamp]
    (let [[innholdet tajm]
       [(str "<html>
              <head>
              <title>" title " :: " blog_title "</title></head>
              <body><h1>" title "</h1>
              <br/>" content "<br/><i>posted " (Date. **(Long/parseLong timestamp)**) "</i>
              <br/><a href=\"" (str blog_url) "\">[main]</a> | 
              <a href=\"" (str blog_url) "/" timestamp ".html\">[permalink]</a>
              </body></html>") (str timestamp".html")]]
                 (spit tajm innholdet)
   )
 )

但是，我仍然建议您找到一种将时间戳作为长整型而不是字符串传递的方法。

Just a small change is necessary:

(defn post
  [title content timestamp]
    (let [[innholdet tajm]
       [(str "<html>
              <head>
              <title>" title " :: " blog_title "</title></head>
              <body><h1>" title "</h1>
              <br/>" content "<br/><i>posted " (Date. **(Long/parseLong timestamp)**) "</i>
              <br/><a href=\"" (str blog_url) "\">[main]</a> | 
              <a href=\"" (str blog_url) "/" timestamp ".html\">[permalink]</a>
              </body></html>") (str timestamp".html")]]
                 (spit tajm innholdet)
   )
 )

However, I would still recommend that you figure out a way to pass in the timestamp as a long instead of a string.

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