From: Joel VanderWerf <vjoel@...>
Date: 2004-05-05T02:14:14+09:00
Subject: Re: Can a program be made to drop into irb?


This is what I use to break from a program into an irb shell. I set my 
app's interrupt handler to call it, and then reset the interrupt handler 
when it is done (where noted). You can go back and forth between app and 
shell with ^C and ^D. I usually add some methods to the object that gets 
passed to start_session: #help, #commands, methods to pipe data to 
gnuplot, etc.

Ara's idea to pass a binding to Workspace.new is great. Changes to 
locals are even persistent after you leave the shell. I'm puzzled about 
why that works--maybe irb detects that the object is a binding?

--

#!/usr/bin/env ruby

require 'irb'
require 'irb/completion'

module IRB
   def IRB.parse_opts
     # Don't touch ARGV, which belongs to the app which called this module.
   end

   def IRB.start_session(object)
     unless $irb
       IRB.setup nil
       ## maybe set some opts here, as in parse_opts in irb/init.rb?
     end

     workspace = WorkSpace.new(object)

     if @CONF[:SCRIPT] ## normally, set by parse_opts
       $irb = Irb.new(workspace, @CONF[:SCRIPT])
     else
       $irb = Irb.new(workspace)
     end

     @CONF[:IRB_RC].call($irb.context) if @CONF[:IRB_RC]
     @CONF[:MAIN_CONTEXT] = $irb.context

     trap 'INT' do
       $irb.signal_handle
     end

     custom_configuration if defined?(IRB.custom_configuration)

     catch :IRB_EXIT do
       $irb.eval_input
     end

     ## might want to reset your app's interrupt handler here
   end
end

class Object
   include IRB::ExtendCommandBundle # so that Marshal.dump works
end

if __FILE__ == $0
   x = Object.new
   puts "\nStarted irb shell for x"
   IRB.start_session(x)
   puts "\nStarted irb shell for current binding"
   IRB.start_session(binding)
   puts "\nExited irb shell"
   p x
end