如何动态查找Clojure函数的元数据？ [英] How do I dynamically find metadata for a Clojure function?

问题描述

说我有以下代码：

 
（defn ^ {：graph-titleFunction 1} func-1 
 [x] 
（do-something-with x））
 
（defn get-graph-title 
 [func] 
 （b）我希望这将返回Function 1，但它返回nil。我认为这源于以下差异，我不完全理解：
 
（meta func-1）
 = > {：ns some-ns-info，：name func-1} 
（meta＃'func-1）
 => {：ns some-ns-info，：name func-1， graph-titleFunction 1} 
 
有人可以向我解释一下吗？
 
 
 
因此，要获取图形标题，您需要从var的元中获取条目：graph-title  
 （defmacro get-graph-title 
 [func] 
 （：graph-title（meta（var〜func））））
 
（get-graph-title func-1）
 => Function 1
  
 
Say I have the following code:
(defn ^{:graph-title "Function 1"} func-1
  [x]
  (do-something-with x))

(defn get-graph-title 
  [func]
  (str
    ((meta func) :graph-title))) 
I expect this to return "Function 1", but it returns nil.  I think this stems from the following difference, which I don't totally comprehend:
(meta func-1)
=>  {:ns some-ns-info, :name func-1}
(meta #'func-1)
=>  {:ns some-ns-info, :name func-1, :graph-title "Function 1"}
Can someone explain this to me?
解决方案
The metadata is attached to the var, not to the function.

Thus, to get the graph title, you have to get the entry :graph-title from the meta of the var. How do you like your macros ?
(defmacro get-graph-title
  [func]
  `(:graph-title (meta (var ~func))))

(get-graph-title func-1)
=> "Function 1"


                        
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