On Saturday, January 24, 2015 at 1:43:15 PM UTC-5, Elric Erkose wrote: > > Hello, > > I have an app which specifies a protocol and a record name. At runtime, it > searches the classpath for files implementing the specification and creates > a map of namespace to instance for each. Before I implemented the protocol, > I just specified function names. I was able to lookup the function names > and call them. After I switched to using a protocol, I get a > CompilerException. > > Here's the question: How do I instantiate a known record from an unknown > namespace? > > Here is the sample code. Thanks for you help. > > ```clojure > (ns proto) > > (defprotocol Proto > (meth [this])) > > ;; use clojure.tools.namespace.find to locate the namespace. > ;; for simplicity, we just def it here. > (def that 'rec) > > (require that) > > ;; the symbol "Rec" is part of the specification > (let [inst (ns-resolve that (symbol "Rec"))] > (when (class? inst) > (println "inst:" (type inst) inst) > ;; => java.lang.Class rec.Rec > > (println "meth:" (meth (new rec.Rec))) > ;; => it works when I know it. > > ;; uncomment this for a CompilerException > ;;(println "meth:" (meth (new inst))) > ;; => CompilerException java.lang.IllegalArgumentException: > ;; Unable to resolve classname: inst, compiling:(proto.clj:21:28) > )) > ``` > > ```clojure > (ns rec > (:require proto)) > > (defrecord Rec [] > proto.Proto > (meth [this] "it works when I know it")) > ``` >
The new special form doesn't evaluate its argument, so "inst" results in looking for a classname of "inst", not whatever inst is bound to. (eval `(new ~inst)) might work though. -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
