CODEWITHSUNDEEP
clojure
BillRobertson42
BillRobertson42

Reputation: 12883

How to invoke superclass' method in a Clojure gen-class method?

I'm trying to create a class that extends input stream Clojure via gen-class. If I want to invoke the parent class' method, how do I do that?

Upvotes: 11

Views: 2518

Answers (2)

Michał Marczyk
Michał Marczyk

Reputation: 84379

From (doc gen-class)1:

:exposes-methods {super-method-name exposed-name, ...}

It is sometimes necessary to call the superclass' implementation of an
overridden method.  Those methods may be exposed and referred in 
the new method implementation by a local name.

So, in order to be able to call the parent's fooBar method, you'd say

(ns my.custom.Foo
  (:gen-class
    ; ...
    :exposes-methods {fooBar parentFooBar}
    ; ...
    ))

Then to implement fooBar:

(defn -fooBar [this]
  (combine-appropriately (.parentFooBar this)
                         other-stuff))

1 In addition to the :gen-class facility provided by ns forms, there is a gen-class macro.

Upvotes: 14

amalloy
amalloy

Reputation: 92147

This is not an answer to your actual question, but I have a little library to let you pretend InputStream is an interface instead of a class (so that you don't need gen-class at all). Check out io.core.InputStream, which lets you reify io.core.InputStreamable and get out a customized InputStream. Whatever instance fields you need can just be locals closed over by the reify.

Upvotes: 1

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