hooks.clj

(ns winston.hooks)

(defn call-hooks [hooks args]
  (doseq [h @hooks]
    (apply (second h) args)))

(defmacro defhook 
  "defines an empty function, used to attach hooks to. All attached hooks must have the same signature"
  [name signature]
  `(let [hooks# (atom [])]
     (defn ~name {:hooks hooks#} [& args#]
       (call-hooks hooks# args#))))

(defn add-hook 
  [hook-var name fn]
  "adds a hook to a function created with defhook. name is a symbol/keyword that can be used to refer to the fn, to remove it later using remove-hook"
  (let [hooks (:hooks (meta hook-var))]
    (swap! hooks conj [name fn])))