Equivalent of Java's toString() for Clojure functions

Question

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 ?

Answer 1

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.

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))

This prints out like #<Title: A Title, URL: http://example.com >

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).