Can't import clojure records

Question

I have created a record like this:

(defrecord User [user-id email])

:but when I try to access it from another name-space I get the error:

(User. "name" "email")

java.lang.IllegalArgumentException: Unable to resolve classname: User

It works when I do:

(oe.model.modelcore.User. "name" "email")

: I know I will need to import the Java class, but is there any way for clojure to do this automatically when I do:

(use 'oe.model.modelcore :reload)

Answer 1

In your question you are creating a record, then invoking the constructor for the class generated as a side effect. To do so you need to import that class as mentioned in another answer.

However, imho the preferred path (since Clojure 1.4) is to use the constructor functions generated by defrecord (here they'll be named ->User and map->User). These functions allow you to avoid the interop forms and just refer in the constructor functions like any other function. By avoiding interop, this is a more portable less-hosty solution:

(ns some-ns 
  (:require [oe.model.modelcore :refer (->User)]))

(def user (->User "name" "email"))

Answer 2

It could be really tricky if you have - (dash) in your name space.

As it turns out there were two errors:

– Importing defrecord from another namespace is not just :use. I had to first :require the namespace, then import the defrecord. This was a trivial problem to solve and I figured it out quickly. Only this did not work in my case

– Dashes “-” and Underscores “_” are a nuisance since we are mixing Lisp with Java. While the file system uses underscores Clojure converts things to dashes. Brilliant.

So to fix the second error I use the follow in the ns block

(ns adder.core
    (:require building-blocks.activity)
    (:import [building_blocks.activity Activity]))

https://cyrax.wordpress.com/2013/07/22/clojure-importrequireuse-defrecord-from-another-namespace/

Answer 3

You have to import the record like this:

(ns some-ns
  (:import [oe.model.modelcore User]))