Arity problem with multi-methods

[Christian Sperandio]

Hi,

I try to define multi-methods but when I call one I get an exception.

I declared the multi-methods like below:

(defmulti new-food-item (fn [food expiration]

                          (if (number? expiration)

                            ::duration

                            ::expiration-date)))

(defmethod new-food-item ::duration [food expiration-duration]

  (let [expiration-date (GregorianCalendar.)]

    (.add expiration-date GregorianCalendar/DAY_OF_MONTH expiration-duration)

    {:name food :expiration-date expiration-date}))

(defmethod new-food-item ::expiration-date [food expiration-date]

  {:name food :expiration-date expiration-date})

And when I do: (new-food-item "tomatoes" 5)

I get this exception:

ArityException Wrong number of args (2) passed to: core$class  clojure.lang.AFn.throwArity (AFn.java:437)

I don't understand where is the problem :/

Some help?

Thank you.

Chris

[grinnbearit]

Hi Chris,

If you change multimethod arities you'll have to def the multimethod to nil or restart the swank/nrepl server. It doesn't update that on recompilation.

Sidhant

[Christian Sperandio]

Thank you !

I became crazy because I didn't see the problem in my code. 

Why is there this issue with multi-methods? (and not with standard functions)

Chris

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[Baishampayan Ghose]

Christian,

defmulti has defonce-like semantics which I guess is to prevent the associated defmethods from being wiped out when the form is recompiled.

Cite - https://github.com/clojure/clojure/blob/master/src/clj/clojure/core.clj#L1622

-BG

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[Art Goldhammer]

Seven years later, a big thank you from me. I was also being driven crazy by this bug. It is insane that this not better documented. In any case it should have been fixed by now.

On Thursday, November 22, 2012 at 2:51:03 AM UTC-5, Baishampayan Ghose wrote:

Christian,

defmulti has defonce-like semantics which I guess is to prevent the associated defmethods from being wiped out when the form is recompiled.

Cite - https://github.com/clojure/clojure/blob/master/src/clj/clojure/core.clj#L1622

-BG

On Wed, Nov 21, 2012 at 11:45 PM, Christian Sperandio <christian...@gmail.com> wrote:

Thank you !

I became crazy because I didn't see the problem in my code. 

Why is there this issue with multi-methods? (and not with standard functions)

Chris

clo...@googlegroups.com

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[Zyxmn Daley Jes]

Thank you all!