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clojurevariadic-functionsclojure-java-interop
qiuxiafei
qiuxiafei

Reputation: 5977

How to handle java variable length arguments in clojure?

I'am wrapping a java lib into clojure, but i have problems dealing with variable length arguments. Say,

TestClass.aStaticFunction(Integer... intList){/*....*/}

How could i call this function in clojure?

Upvotes: 47

Views: 9343

Answers (3)

jittakal
jittakal

Reputation: 919

(TestClass/aStaticFunction (to-array '(1 2 3 4 5)))

For e.g. 

(java.util.Arrays/asList (to-array '(1 2 3 4 5)))

Upvotes: 5

mikera
mikera

Reputation: 106351

Java variable length arguments actually want an array as input.

So in Clojure the call should be something like:

(TestClass/aStaticFunction (into-array Integer some-sequence-of-integers))

Upvotes: 9

Zach L
Zach L

Reputation: 16262

Since Java varargs are actually arrays, you can call vararg functions in Clojure by passing an array.

You could convert a Clojure seq (maybe by using Clojure's variety of variable argument functions) into an array:

 (TestClass/aStaticFunction (into-array Integer [(int 1),(int 2)]))

or 

(defn a-static-function-wrapper [& args]
  (TestClass/aStaticFunction (into-array Integer args))

Or make an array and set its indices manually

(TestClass/aStaticFunction (doto (make-array Integer 3)
                              (aset 0 first-element)
                              (aset 1 second-element)
                              (aset 2 third-element)))

Upvotes: 64

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