Question

我正在尝试使用Prismatic / Schema匹配以下序列：

[{:n "some text"}] ; => valid

和

[{:k "some text"} {:n "some text"}] ; => valid

我尝试过：

(s/def Elem3
  {:k s/Str})

(s/def Elem2
  {:n s/Str})

(s/def Elem
  [(s/optional Elem2 "elem2") Elem3])

(s/validate Elem [{:k "huji"}])
;; =>
;; Value does not match schema: [(named {:n missing-required-key, :k
;; disallowed-key} "elem2")]

(s/def Elem
  [(s/maybe Elem2) Elem3])

(s/validate Elem [{:k "huji"}])
;; =>
;; [(maybe {:n Str}) {:k java.lang.String}] is not a valid sequence
;; schema; a valid sequence schema consists of zero or more `one`
;; elements, followed by zero or more `optional` elements, followed by
;; an optional schema that will match the remaining elements.

(s/defrecord ElemOption1
  [elem3 :- Elem3])

(s/defrecord ElemOption2
    [elem2 :- Elem2
     elem3 :- Elem3])

(s/def Elem
  (s/conditional
   #(= 2 (count %)) ElemOption2
   :else ElemOption1))

(s/validate Elem [{:k "huji"}])
;; =>
;; Value does not match schema: (not (instance?
;;  peg_dsl.standard_app.ElemOption1 [{:k "huji"}]))

主要问题是我不明白写什么方式允许省略指定向量的第一个元素的模式。匹配上述两个向量的正确方法是什么？

Answer 1

你第一次尝试的问题是从一开始可选意味着它期望{：k s / Str}或者没有任何东西，而且它正在看到 {:n s/Str}，所以显然不对。

你的第二次尝试有两个问题。 Maybe可以是价值或nil，但它需要存在。你也没有写过序列模式正确。但是序列模式的问题是元素需要按顺序s/one* s/optional*和你想要s/optional s/one。

你的第三次尝试更接近，使用条件，但你是无法匹配，因为您没有验证的实例记录，你正在验证地图。

解决方案如下所示：

(def ElemKNList [(s/one {:k s/Str} "k") (s/one {:n s/Str} "n")])
(def ElemNList [(s/one {:n s/Str} "n")])

(def Elem (s/conditional #(= 2 (count %)) ElemKNList 
                         :else ElemNList))

(s/validate Elem [{:k "huji"} {:n "huji"}])    
    => [{:k "huji"} {:n "huji"}]
(s/validate Elem [{:n "huji"}])
    => [{:n "huji"}]          
(s/validate Elem [{:k "huji"}])
    => ExceptionInfo Value does not match schema: [(named {:n missing-required-key, :k disallowed-key} "n")]  schema.core/validator/fn--18435 (core.clj:151)

可选元素按顺序排列

1 个答案: