Clojure，Aspects，Defprotocol，Defrecord [英] Clojure, Aspects, Defprotocol, Defrecord

问题描述

(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，我想输出：

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

不幸的是，这并不会发生，因为上面的代码不能编译。什么是实现这个的最好方法？

Unfortuantely, this does not happen since the above code does not compile. What is the best way to achieve "this" ?

在这里，我的意思是我有一些功能，我想成为协议的一部分，我想对所有记录有一个实现它，我希望这个函数可以访问记录实现的专门函数。

Where by "this", I mean I have some function that I want to be part of a protocol, I want to have one implementation of it for all records, and I want this function to have access to specialized functions that records implement.

（什么是clojure这样做？ ）

(What is the clojure way of doing this?)

推荐答案

协议就像Java接口，他们不能为他们的方法提供实现。但这个工程：

Protocols are like Java interfaces, they cannot provide implementation for their methods. But this works:

(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.

这篇关于Clojure，Aspects，Defprotocol，Defrecord的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！