Best way to call Clojure function with named/default args from Java

Question

When calling a Clojure function from Java, what's the best way to specify named arguments to the function?

I have the following function:

(defn myFn [a b & {:keys [c d] :or {c 1 d 2}}]
   ; do something
   )

And I currently call it from Java with lines like this:

IFn myFn = Clojure.var("my.namespace", "myFn");
myFn.invoke(5, 6, Clojure.read(":c"), 7, Clojure.read(":d"), 8);

I find the Clojure.read... parts of the above statement verbose. Is there a simpler way to make this call?

Because the arguments are optional. I also call the same function without c and d. — Jason
– Jason, Commented Oct 23, 2015 at 15:01

Davyzhu · Accepted Answer · 2015-10-27 03:37:37Z

5

The question is not about how to pass named argument, but how to create keywords in Java code:

import clojure.lang.Keyword;
// others omitted...
myFn.invoke(5, 6, Keyword.find("c"), 7, Keyword.find("d"), 8);

Clojure.read would be considered too cumbersome for the task and too dangerous as it can read in any code.

edited Oct 27, 2015 at 3:37

answered Oct 12, 2015 at 3:28

Davyzhu

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4 Comments

Jason Over a year ago

You seem to have a typo: invokde should be invoke.

Jason Over a year ago

This is still verbose. Is there anything shorter? Or is there a better way to design this interface between clojure and Java? Like using clojure prototypes or multi-methods?

Davyzhu Over a year ago

@Jason Thanks, fixed. Regarding the further question, I don't see any shorter/better ways than this method invocation with arguments prepared. Not much redundancy here to be removed.

Jason Over a year ago

Hmmm... I feel an unsettling dissatisfaction with this answer. I suppose if I factored out the Keyword.find("c") and "d" bits into constants then they can be reused and the call to invoke will be shorter. So I accept your answer, but part of me is still waiting for something better :-)

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