Can you monkey-patch the meta function itself to draw from a map of object
to meta?
On Saturday, August 30, 2014, Francis Avila <franci...@gmail.com> wrote:
> It would probably help if you said more about the source of this
> atom-holding object. Is it a plain Java class? A deftype/defrecord? Is it
> final?
>
>
> If you can control the construction of this object and its class is not
> final, you can subclass it and add an IObj implementation. (Note that most,
> maybe all clojure ways of creating classes create final classes, so this
> technique won't work.) The easiest way to subclass is with `proxy`:
>
> (defn meta-AtomHolder [atom-value metadata]
> (proxy [AtomHolderClass clojure.lang.IObj] ;; [superclass, new
> interfaces]
> [atom-value] ;; constructor args
> (meta [] metadata) ;; subclass method
> (withMeta [newmeta] (meta-AtomHolder newmeta))))
> => (var user/meta-AtomHolder)
> (meta-AtomHolder (atom "x") {})
> => #<AtomHolderClass$IObj$40298964
> user.proxy$AtomHolderClass$IObj$40298964@302c28cc>
> (meta (meta-AtomHolder (atom "x") {}))
> => {}
> (meta (with-meta (meta-AtomHolder (atom "x") {}) {:a 1}))
> => {:a 1}
>
> If the parent class is final or you can't construct the object yourself,
> you need to delegate method calls from one instance to this object
> instance. I think this is hard-but-not-impossible in java, but I'm not sure.
>
> (Clojurescript has `specify`, which does exactly what you want, but only
> exists because delegation between instances in javascript is trivial.)
>
> On Friday, August 29, 2014 10:16:05 PM UTC-5, Atamert Ölçgen wrote:
>>
>> Obviously I can't.
>>
>> But I need to add this capability to an object. During testing I attach
>> meta to this object that contains an atom. Then I pass this object to other
>> functions, known in runtime. I can't use a dynamic var because all this
>> happens within a mock function that may be retried and run in different
>> threads.
>>
>> I have seen this: http://stackoverflow.com/questions/20724219/
>> simplest-possible-clojure-object-that-can-accept-a-primitive-and-metadata
>> but can't deref it since I can't change the functions that will use it
>> later. If I wrap this object I need to be able to delegate all of its
>> functionality to the original object.
>>
>> I hope this all is not too vague. The code I'm working on is not online
>> yet. But it's for clecs (https://github.com/muhuk/clecs/), I'm adding
>> quickcheck to compare different world implementations.
>>
>>
>> --
>> Kind Regards,
>> Atamert Ölçgen
>>
>> -+-
>> --+
>> +++
>>
>> www.muhuk.com
>>
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