问在clojure中处理多个数据层

EN

(ns app.db-api
  (:require [app.old-api]
            [app.new-api]
            [app.config :refer [env]]))

;; Define placeholder functions that are later interned to point at either
;; new or old API. The corresponding functions are defined and implemented in
;; old-api and new-api
(defn get-user [user-id])
(defn create-user [user-name])

;; Iterate through defined functions in this namespace and intern
;; them to the corresponding functions in the new or old API, as
;; configured by the :db-api environment variable
(doseq [f (keys (ns-publics *ns*))]
  (let [x (symbol f)
        y (eval (symbol (str "app." (env :db-api) "/" f)))]
    (intern *ns* x y)))