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comp.lang.ruby

Restoring global variables?

Bertram Scharpf

1/30/2005 9:48:00 PM

Hi,

do I have any possibiliy to save and restore global
and instance variables? I think of something like:

user@host$ cat l.rb
class C ; @@i = 0 ; end
$g = ""

cache_globals { load 'm.rb' }
assert $g == "" and C.instance_eval { @@i.zero? }

user@host$ cat m.rb
C.instance_eval { @@i += 99 }
$g << "foo"
user@host$

There are several workarounds, for example starting another
process. What is the smartest way to do it?

Thanks in advance.

Bertram

--
Bertram Scharpf
Stuttgart, Deutschland/Germany
http://www.bertram-...
2 Answers

Robert Klemme

1/30/2005 11:06:00 PM

0


"Bertram Scharpf" <lists@bertram-scharpf.de> schrieb im Newsbeitrag
news:20050130214711.GA30470@homer.bertram-scharpf...
> Hi,
>
> do I have any possibiliy to save and restore global
> and instance variables? I think of something like:
>
> user@host$ cat l.rb
> class C ; @@i = 0 ; end
> $g = ""
>
> cache_globals { load 'm.rb' }
> assert $g == "" and C.instance_eval { @@i.zero? }
>
> user@host$ cat m.rb
> C.instance_eval { @@i += 99 }
> $g << "foo"
> user@host$
>
> There are several workarounds, for example starting another
> process. What is the smartest way to do it?

This is one way that's better than another process.

module Kernel
private
def cache_globals
store = {}
global_variables.each {|v| store[v] = eval(v)}
begin
return yield
ensure
store.each do |n,v|
begin
eval "#{n}=v"
rescue NameError, SyntaxError, ArgumentError
# ignore
end
end
end
end
end

$f = 0
p $f
cg { $f = 100; p $f }
p $f

You can also create something with #trace_var:
http://www.ruby-doc.org/core/classes/Kernel.ht...

Kind regards

robert

Bertram Scharpf

1/31/2005 7:58:00 AM

0

Hi,

Am Montag, 31. Jan 2005, 08:10:47 +0900 schrieb Robert Klemme:
>
> "Bertram Scharpf" <lists@bertram-scharpf.de> schrieb im Newsbeitrag
> news:20050130214711.GA30470@homer.bertram-scharpf...
> >do I have any possibiliy to save and restore global
> >and instance variables? I think of something like:
> >
> > user@host$ cat l.rb
> > class C ; @@i = 0 ; end
> > $g = ""
> >
> > cache_globals { load 'm.rb' }
> > assert $g == "" and C.instance_eval { @@i.zero? }
> >
> > user@host$ cat m.rb
> > C.instance_eval { @@i += 99 }
> > $g << "foo"
> > user@host$
> >
> >There are several workarounds, for example starting another
> >process. What is the smartest way to do it?
>
> This is one way that's better than another process.
>
> module Kernel
> private
> def cache_globals
> store = {}
> global_variables.each {|v| store[v] = eval(v)}
> begin
> return yield
> ensure
> store.each do |n,v|
> begin
> eval "#{n}=v"
> rescue NameError, SyntaxError, ArgumentError
> # ignore
> end
> end
> end
> end
> end
>
> $f = 0
> p $f
> cg { $f = 100; p $f }
> p $f

Another nice workaround. Two caveats:

* Newly created variables aren't destroyed.
* side effects:

irb(main):002:0> eq=eval '$='
=> false
irb(main):003:0> eval '$= = eq'
(eval):1: warning: modifying $= is deprecated
=> false

> You can also create something with #trace_var:
> http://www.ruby-doc.org/core/classes/Kernel.ht...

Instantiating about 50 trap routines? No. Besides that, the
above solution could be bypassed using a trace. It's a
security question I asked.

Thanks very much anyway, so far.

Bertram

--
Bertram Scharpf
Stuttgart, Deutschland/Germany
http://www.bertram-...