Clojure中的重复结构

Question

在"Web开发与Clojure"一书中所说的代码

(defn registration-page []
    (layout/common
        (form-to [:post "/register"]
            (label "id" "screen name")
            (text-field "id")
            [:br]
            (label "pass" "password")
            (password-field "pass")
            [:br]
            (label "pass1" "retype password")
            (password-field "pass1")
            [:br]
            (submit-button "create account"))))

可以使用辅助函数重写如下:

(defn control [field name text]
  (list (on-error name format-error)
        (label name text)
        (field name)
        [:br]))

(defn registration-page []
  (layout/common
    (form-to [:post "/register"]
      (control text-field :id "screen name")
      (control password-field :pass "Password")
      (control password-field :pass1 "Retype Password")
      (submit-button "Create Account"))))

我的问题是:在替代代码中,为什么参数名称的值不是字符串？例如,为什么(控制文本字段:id "屏幕名称"),而不是(控制文本字段"id" "屏幕名称")？

Answer 1

我不熟悉Hiccup,我没有你提到的那本书.但是通过阅读Hiccup源代码,您可以找到:

Label正在调用make-id函数,它调用as-str.看看那个功能,看看它在做什么.

(defn ^String as-str
  "Converts its arguments into a string using to-str."
  [& xs]
  (apply str (map to-str xs)))

这将引导您使用ToString协议.

在您发布的代码段中传递字符串而不是关键字,看看发生了什么!

源代码是我们可以拥有的最佳文档!