From: Robert Klemme <bob.news@...>
Date: 2003-06-25T17:15:56+09:00
Subject: Re: Inspecting a caller environment?


"Luigi Ballabio" <luigi.ballabio@fastwebnet.it> schrieb im Newsbeitrag
news:pan.2003.06.24.17.07.18.904137@fastwebnet.it...
> On Wed, 25 Jun 2003 00:09:31 +0900, Robert Klemme wrote:
>
> > "Luigi Ballabio" <luigi.ballabio@fastwebnet.it> schrieb im Newsbeitrag
> > news:pan.2003.06.24.14.18.21.963302@fastwebnet.it...
> >> Hi all,
> >> having to design a usable environment for non
> >> extremely-computer-literate users, I'd like them to fire
> >> up irb with some default options via an alias and write:
> >>
> >> Foo> foo = 'life'
> >> Foo> bar = 'the universe'
> >> Foo> baz = 'everything'
> >> Foo> calculate
> >>      ==> 42
> >> Foo>
> >>
> >
> > If you can guess the variable names you can do:
> >
> > b = eval 'x'
>
> Hmm, not if calculate is defined in another module, I think...

You can access local variables under certain circumstances, i.e., if you
get a binding from that environment:

irb(main):001:0> def bind()
irb(main):002:1>   foo = "value of foo"
irb(main):003:1>   binding
irb(main):004:1> end
nil
irb(main):005:0>
irb(main):006:0* b = bind
#<Binding:0x2ab2aa0>
irb(main):007:0>
irb(main):008:0* eval "foo", b
"value of foo"
irb(main):009:0>

However, i guess you are right, because it will be difficult to get a
binding from the prompt's context.

> > A simple solution to your problem is to use instance variables like
this:
> >
> > irb(main):001:0> @foo = 'life'
> > "life"
> > irb(main):002:0> @bar = 'the universe'
> > "the universe"
> > irb(main):003:0> @baz = 'everything'
> > "everything"
> > irb(main):004:0>
> > irb(main):005:0* instance_variables
> > ["@bar", "@foo", "@baz"]
> > irb(main):006:0> instance_variables.map{|var| eval var}
> > ["the universe", "life", "everything"]
> > irb(main):007:0>
>
> I like this one! Again, the eval part won't work if calculate is
> defined elsewhere, but I do know the variable names, so I can just
> use them...

No, that definitely works anywhere.  You just need to get the object
reference of the instance that has the variables:

irb(main):001:0> class Foo
irb(main):002:1>   # instances can have arbitrary variables
irb(main):003:1*   def set(name, var)
irb(main):004:2>     instance_eval "@#{name} = var"
irb(main):005:2>   end
irb(main):006:1> end
nil
irb(main):007:0>
irb(main):008:0* f = Foo.new
#<Foo:0x2aadcd0>
irb(main):009:0>
irb(main):010:0* f.instance_variables
[]
irb(main):011:0> f.instance_variables.each {|v| puts "#{v} =
#{f.instance_eval(
v ).inspect}" }
[]
irb(main):012:0>
irb(main):013:0* f.set "foo", "xx"
"xx"
irb(main):014:0> f.instance_variables
["@foo"]
irb(main):015:0> f.instance_variables.each {|v| puts "#{v} =
#{f.instance_eval(
v ).inspect}" }
@foo = "xx"
["@foo"]
irb(main):016:0>
irb(main):017:0* f.set "bar", "baz"
"baz"
irb(main):018:0> f.instance_variables
["@bar", "@foo"]
irb(main):019:0> f.instance_variables.each {|v| puts "#{v} =
#{f.instance_eval(
v ).inspect}" }
@bar = "baz"
@foo = "xx"
["@bar", "@foo"]
irb(main):020:0>

Regards

    robert