Hi,
I would like to be able to add metadata to arbitrary java objects that
have already been instantiated. I know that you can use proxy to add
metadata to objects that you create but in my case the object already
exists (i.e. it is returned from another method call outside of my control).
It seems like the best solution would be to create a delegate
class/object that wraps the original one. Being able to write something
like this would be ideal:
(defn wrap-with-meta
([obj]
(wrap-with-meta obj nil))
([obj meta]
(delegate obj
clojure.lang.IObj
(withMeta [this new-meta] (wrap-with-meta
obj
new-meta))
(meta [this] meta))))
The delegate function would operate very similar to proxy, but instead
of taking a class it takes an object. A class would be created that
extends the object's class, just like a class is generated for proxy.
However, instead of stubs being generated that call super the stubs
would delegate to the given object. (Also note, I am also using
reify-like syntax since I prefer that to the syntax in proxy.)
I'm curious to hear people's thoughts on this approach. I'd also be
really interested to see how other people have addressed this in the
past (I doubt I'm the first one to run into this).
I know that clojure mentality is to avoid wrappers, but I don't see this
as being much different than what proxy already does. Of course, I may
be missing something... if so, please enlighten me. :)
Thanks,
Ben
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