Addendum to my previous post; (set! *warn-on-reflection* true) true user=> (.compareTo myComp :d) Reflection warning, NO_SOURCE_PATH:10 - call to compareTo can't be resolved. 1 user=> (.compareTo ^Comparable myComp :d) 1
user=> (class myComp) user$reify__1 (instance? Comparable myComp) true On Wed, Sep 1, 2010 at 4:33 PM, Adrian Cuthbertson <adrian.cuthbert...@gmail.com> wrote: > Have a look at Stuart Halloway's video on protocols; > http://vimeo.com/11236603 > and also clojure.core.protocols.clj in the 1.2 source code. > A general google on clojure protocols also brings up some blogs in > which various people have some good examples and explanations. > > Also note that deftype of course works for existing java interfaces as well. > > Reify is also useful for implementing anonymous implementations of > java library interfaces. Here's a not very useful quick example of > reifying the java Comparable interface; > > (def myComp (reify java.lang.Comparable (^int compareTo [_ k] (condp = > k :a -1 :b 0 1)))) > #'user/myComp > user=> (.compareTo myComp :a) > -1 > user=> (.compareTo myComp :b) > 0 > user=> (.compareTo myComp :c) > 1 > user=> (.compareTo myComp :d) > 1 > > and another implementing and executing the java Executor interface. > > (import 'java.util.concurrent.Executor) > java.util.concurrent.Executor > user=> > (let [f (fn[] (println "hello")) > thrd (reify Executor (^void execute [_ ^Runnable cmd] (.run cmd)))] > (.execute thrd f)) > hello > nil > > These are really useful things if you do a lot of clojure/java work > (which I do). > > > > On Wed, Sep 1, 2010 at 2:59 PM, Albert Cardona <sapri...@gmail.com> wrote: >> Hi Adrian, >> >> Thanks for the explanations. Indeed I was assuming a protocol would >> work like an interface, so I may just as well use definterface >> directly. >> >> To date, protocols confuse me a bit--I have no reference for it in my >> head. I see how you use them like multimethods and that's very neat. >> Thanks for showing how to use them. >> >> It's a pity that definterface has to use "test_it" (note the >> underscore), as you pointed out. I guess it has to do with >> definterface having a note saying "for now, rely on gen-class" or some >> such, in its declaration. >> >> Albert >> >> -- >> http://albert.rierol.net >> >> -- -- 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
