clj validators

validators.clj

(defn validator
  [msg fn]
  (letfn [(validate [& args]
            (apply fn args))]
    (with-meta validate {:msg msg})))

(defn checker
  [& validators]
  (fn [v]
    (clojure.core/reduce (fn [errors validator]
              (if (validator v)
                errors
                (conj errors (:msg (meta validator))))) [] validators)))


;; example
(def validate (checker (validator "must not be zero" #(not (zero? %)))))
(validate 1) ;; -> []
(validate 0) ;; -> ["must not be zero"]


(def validate (checker (validator "must be positive" pos?)
                       (validator "must be an integer" integer?)
                       (validator "must be > 5" #(< 5 %))))

(validate -1) ;; -> ["must be positive" "must be > 5"]
(validate 4.0) ;; -> ["must be an integer" "must be > 5"]
(validate 6) ;; -> []

(if (seq? (validate value))
  (do-invalid)
  (do-valid))