On Fri, Jul 6, 2012 at 8:48 AM, Maksym Parkachov <lazy.gop...@gmail.com> wrote:
> I'm trying version 1.7 preview, which works great and fast btw., and
> becoming a lot of warning concerning singleton on non-persistent Java
> type.
>
> The pattern, I'm using:
>
> require 'java'
> java_import java.util.ArrayList
>
> class ArrayList
> def psize
> puts size
> end
> end
This part is ok; reopening Java classes is fine.
> list = ArrayList.new
>
> list.instance_exec do
> psize
> add 10
> psize
> end
This part does indeed cause a singleton to be created, under both MRI
and JRuby. That is unfortunately how instance_exec and instance_eval
work.
> I understand, that singleton class will be generated, if I change
> class definition with instance_exec, but executing methods should not
> create singleton ? Or should it ?
It does indeed. I had forgotten this myself, but as far as I can tell
the singleton is created right away just in case you *do* define
methods.
It may be possible to avoid creating the singleton, but I'm not sure
we'd be safe in doing so since MRI would stil do it.
> I would really appreciate suggestions on how to achieve above
> mentioned pattern, or maybe fix warning or generation of singleton.
At the moment, I know of no way to get exactly what you want, but I
will experiment a bit.
- Charlie
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