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clojurepre

how to raise a exception in clojure pre-expr?

clojure's pre-expr seems cool, but does it possible if I want to raise an Exception when the :pre is false?

thanks.

Solution

  • You can use Dire instead 

    (ns mytask
  (:require [dire.core :refer [with-precondition! with-handler!]]))

(defn add-one [n]
  (inc n))

(with-precondition! #'add-one
  "An optional docstring."
  ;;; Name of the precondition
  :not-two
  (fn [n & args]
    (not= n 2)))

(with-handler! #'add-one
  {:precondition :not-two}
  (fn [e & args] (apply str "Precondition failure for argument list: " (vector args))))

(add-one 2) ; => "Precondition failure for argument list: (2)"