遍歷矢量樹

Question

欲遍歷表示打嗝數據結構的載體樹：

[:div {:class "special"} [:btn-grp '("Hello" "Hi")]] 

然後我想派遣於載體上的關鍵字，如果多重方法已爲關鍵字定義，然後它會返回另一組矢量，它將替換原始標記。

例如，上述結構會被變換爲：

[:div {:class "special"} [:div [:button "Hello"] [:button "Hi"]]] 

定製多重方法將收到列表（「你好」，「喜」）作爲參數。它會返回包含按鈕的div。

我如何寫穿越載體與形式作爲參數一切分派的關鍵字，然後返回的形式代替當前形式的功能？

Answer 1

(ns customtags 
    (:require [clojure.walk :as walk])) 

(def customtags (atom {})) 

(defn add-custom-tag [tag f] 
    (swap! customtags assoc tag f)) 

(defn try-transform [[tag & params :as coll]] 
    (if-let [f (get @customtags tag)] 
    (apply f params) 
    coll)) 

(defmacro defcustomtag [tag params & body] 
    `(add-custom-tag ~tag (fn ~params ~@body))) 

(defn apply-custom-tags [coll] 
    (walk/prewalk 
    (fn [x] 
     (if (vector? x) 
     (try-transform x) 
     x)) coll)) 

使用它：

(require '[customtags :as ct]) 
(ct/defcustomtag :btn-grp [& coll] (into [:div] (map (fn [x] [:button x]) coll))) 
(ct/defcustomtag :button [name] [:input {:type "button" :id name}]) 

(def data [:div {:class "special"} [:btn-grp "Hello" "Hi"]]) 

(ct/apply-custom-tags data) 
[:div {:class "special"} [:div [:input {:type "button", :id "Hello"}] [:input {:type "button", :id "Hi"}]]]