From: Karel Michek <KMichek@...>
Date: 2006-08-13T14:35:43+09:00
Subject: Re: newbie question: how to create variable


> ------------ P�vodn� zpr�va ------------
> Od:  <dblack@wobblini.net>
> P�edm�t: Re: newbie question: how to create variable
> Datum: 12.8.2006 14:27:31
> ----------------------------------------
> Hi --
> 
> On Sat, 12 Aug 2006, Mr Pinto wrote:
> 
> > On Aug 11, 2006, at 12:55 PM, Robert Klemme wrote:
> >
> >> Karel Michek wrote:
> >>> Hi,
> >>> how to create variable in the method that accepts string as name of the 
> >>> variable and the object? Something like this:
> >>> class InterpreterCallback     
> >>>   def set_object(name, value)
> >>>      #do something here
> >> 
> >> instance_variable_set("@#{name}", value)
> >>>    end
> >>> end
> >>> $callback = InterpreterCallback.new()
> >>> $callback.set_object("var", 3)
> >>> puts var
> >>>>>> 3
> >
> > Depending on what you're trying to do, you might be able to use a simple eval
> 
> > statement:
> > irb(main):001:0> name="var"
> > => "var"
> > irb(main):002:0> value="3"
> > => "3"
> > irb(main):003:0> eval "#{name} = value"
> > => "3"
> > irb(main):004:0> var
> > => "3"
> 
> That only works in irb.  With ruby you'll get:
> 
>   ruby -e 'name="var"; value="3"; eval("#{name}=#{value}"); var'
>    -e:1: undefined local variable or method `var' for main:Object
>    (NameError)
> 
> 
> David
> 
> 

None of this actually works quite well for me. I am using SWIG directors to embed ruby (and python, perl) into C# application trough C++ layer. value actually wraps C++ object . InterpreterCallback actually extends c++ class and I am calling set_object() from C++ - set_object("editor", getEditor() ) - "editor" then can be used in the global namespace for scripting convenience:

editor.DrawGrid

I actually get it working with 

    def set_object(var, value)
      eval("def #{var}; $#{var}; end; proc{|_v| $#{var} = _v}", TOPLEVEL_BINDING).call(value)
    end

but it goes through global variable. I believe there is simpler way how to do this.
Kind regards,
Karel