Clojure、方面、Defprotocol、Defrecord

Question

(defprotocol IAnimal "IAnimal"
  (report [o]
    (println (type o) " reporting.\n")
    (inner-report o)
    (println (type o) " out.\n")))

(defrecord Dog [] IAnimal
  (inner-report [o]
    (println "Woof Woof.\n")))

(defrecord Cat [] IAnimal
  (inner-report [o]
    (println "Meow Meow.\n")))

(defrecord Vampire [] IAnimal
  (inner-report [o]
    (println "I don't sparkle.\n")))

现在，我希望它输出:

Dog reporting.
Woof Woof.
Dog out.
Cat reporting.
Meow Meow.
Cat out.
Vampire reporting.
I don't sparkle.
Vampire out.

不幸的是，这种情况不会发生，因为上面的代码无法编译。实现“这个”的最佳方法是什么？

这里的“这个”，我的意思是我有一些函数想要成为协议(protocol)的一部分，我想要为所有记录有一个它的实现，并且我希望这个函数能够访问记录的专门函数实现。

(clojure 的方法是什么？)

Answer 1

协议(protocol)就像 Java 接口(interface)，它们不能提供其方法的实现。但这是有效的:

(defn report [o]
  (println (type o) " reporting.\n")
  (inner-report o)
  (println (type o) " out.\n"))

(defprotocol IAnimal
  "the animal protocol"
  (inner-report [o] "a report"))

(defrecord Dog []
  IAnimal
  (inner-report [o]
    (println "Woof Woof.\n")))

(defrecord Cat []
  IAnimal
  (inner-report [o]
    (println "Meow Meow.\n")))

(defrecord Vampire []
  IAnimal
  (inner-report [o]
    (println "I don't sparkle.\n")))

(report (new Cat))
;; user.Cat reporting.
;; Meow Meow.
;; user.Cat out.