Comments on Jay Fields' Thoughts: Clojure & Java Interop

Hi, In proxy vs. reify, I think it's worth me...

2011-12-28T22:19:27.648-05:00

Hi,

In proxy vs. reify, I think it's worth mentioning that the main difference is that proxy allows you to sub-class existing classes, not just implement interfaces. You mostly need proxy when you're working with old, yucky, inheritance-heavy Java libs. Otherwise, reify is almost always a better choice because it doesn't mess with "this", and plays nicely with protocols as well as interfaces.

Cheers,

Dave

@tapichu, You're welcome. Thanks for commentin...

2011-12-28T13:58:09.371-05:00

@tapichu,
You're welcome. Thanks for commenting.

Your example code will work just fine - RT.var returns a clojure.lang.Var, which is also a IFn, so there's no issue there; however, since you're just passing fib into invoke (which takes an Object) I would just leave fib as a clojure.lang.Var or I'd define it as an Object. I can't see any reason to cast it to an IFn.

When I first started doing clojure I used ..; however, these days I use -> exclusively. I mean't to put that in the blog entry as well, but forgot. Thanks for the reminder. It's worth knowing both, but I prefer -> since it works for Java as well as Clojure. The equivalent version of your example would be:

(-> (System/getProperties) (.get "os.name"))

Cheers, Jay

Thanks for the post, I'm just starting to lear...

2011-12-28T13:42:34.241-05:00

Thanks for the post, I'm just starting to learn Clojure and I was wondering how to execute Clojure from Java.

Would this be a good way of working with lazy sequences?

RT.loadResourceScript("interop/core.clj");
clojure.lang.IFn nth = (clojure.lang.IFn) RT.var("clojure.core", "nth");
clojure.lang.IFn fib = (clojure.lang.IFn) RT.var("interop.core", "fib");
System.out.println(nth.invoke(fib, 30));

Oh and something you didn't mention that I like about Clojure & Java interop is the '..' macro to chain method calls:

(.. System (getProperties) (get "os.name"))

Cheers