Restoring global variables?

[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?

Thanks in advance.

Bertram

 

[Robert Klemme]

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.html#M001741

Kind regards

robert

 

[Bertram Scharpf]

Hi,

Am Montag, 31. Jan 2005, 08:10:47 +0900 schrieb Robert Klemme:

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.html#M001741

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