Re: [jruby-dev] Singleton object with instance_exec

[Rodrigo Rosenfeld Rosas]

Em 06-07-2012 10:48, Maksym Parkachov escreveu:

Hi developers,

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

list = ArrayList.new

list.instance_exec do
   psize
   add 10
   psize
end

While, currently it works, it generates warning:
jruby ss.rb
ss.rb:1 warning: singleton on non-persistent Java type
Java::JavaUtil::ArrayList (http://wiki.jruby.org/Persistence)
0
1

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 ?

While, of course, I could use:

list.psize
list.add 10
list.psize

i wanted to avoid it, because I have a lot of code which should be
executed like this.

If the only reason is to avoid lots of typing, you could do something like:

myLongListNameIDontWantToRepeat.tap do |l|
  l.psize
  l.add 10
  l.psize
  ...
end

Does it help a bit?

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