与Java的toString()等效于Clojure函数 [英] Equivalent of Java's toString() for Clojure functions

问题描述

我正在使用的某些Java代码在Clojure函数对象上调用toString()，它返回类似#<ns$something something.something$something@7ce1eae7>>的东西-我想返回其他东西...大概是有一种方法可以在函数中包含一些元数据，因此它们对象的toString()返回它，而不是?

some Java code I'm using invokes toString() on my Clojure function objects, which return something like #<ns$something something.something$something@7ce1eae7>>- I want to return something else...presumably there's a way to include some metadata in the functions so their objects' toString() returns that instead ?

推荐答案

如果只想使对象的REPL打印输出更有意义，则可以为所涉及的类实现defmethod print-method.

If you just want to make the REPL print-out of your objects more meaningful, you can implement a defmethod print-method for the class in question.

这是我最近编写的一些代码的简化版本；这使Selenium-WebDriver WebDriver对象的REPL打印输出更有意义:

Here's a shortened version of some code I've written recently; this makes the REPL print-out of a Selenium-WebDriver WebDriver object more meaningful:

(defmethod print-method WebDriver
[o w]
(print-simple
 (str "#<" "Title: "    (.getTitle o) ", "
           "URL: "      (.getCurrentUrl o) " >")
  w))

打印出来的像#<Title: A Title, URL: http://example.com >

在这里，WebDriver代表一个类；您可以通过为相应的类实现print-method来轻松地对内置Clojure数据结构执行此操作(Clojure的喜悦功能为clojure.lang.PersistentQueue提供了print-method，默认情况下没有漂亮的表示形式).上面的o是您要处理的实际对象，而w是编写器(这些打印功能需要).

Here, WebDriver represents a class; you can just as easily do this for built-in Clojure data structures by implementing print-method for the appropriate class (The Joy of Clojure features a print-method for clojure.lang.PersistentQueue which has no nice representation by default). The o above is the actual object you're dealing with and w is a writer (required by these kinds of print functions).

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