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
>
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