From: Joel VanderWerf <vjoel@...>
Date: 2007-03-18T01:42:42+09:00
Subject: Re: IRB as test interface to existing object

Brian Candler wrote:
> Hello,
> 
> I have some object classes to which I want to add an interactive
> command-line shell for testing. At the moment, at the end of the source file
> I have something like
> 
> if __FILE__ == $0
>   obj = MyClass.new(*ARGV)
>   CLI.run(obj, "MyClass> ")
> end
> 
> Now, I had started writing a CLI module which reads lines from stdin, splits
> them into an array, runs obj.send(*args), and prints the response. Then it
> occurred to me that this is what IRB is for. But I don't know how to start
> IRB in such a way that the default "self" receiver is an object which I
> created.
> 
> Here's an example of what I'd like to end up with:
> 
> class Foo
>   attr_reader :addr
>   def initialize(addr)
>     @addr = addr
>   end
> 
>   def do_stuff(n)
>     n.times { puts "doing stuff with #{@addr}" }
>   end
> end
> 
> if __FILE__ == $0
>   obj = Foo.new(*ARGV)
>   prompt = "Foo(#{obj.addr})> "
>   IRB.run(obj, prompt)          # <<<--- what do I put here?
> end
> 
> $ ruby foo.rb 127.0.0.1
> Foo(127.0.0.1)> do_stuff 3
> doing stuff with 127.0.0.1
> doing stuff with 127.0.0.1
> doing stuff with 127.0.0.1
> nil
> Foo(127.0.0.1)> 
> 
> Reading the irb manpage, I can see that you can use the 'irb' command
> (interactively) to set the default receiver in a subshell:
> 
> irb(main):012:0> obj = Foo.new("127.0.0.1")
> => #<Foo:0xb7c46730 @addr="127.0.0.1">
> irb(main):013:0> irb obj
> irb#1(#<Foo:0xb7c46730>):001:0> do_stuff 3
> doing stuff with 127.0.0.1
> doing stuff with 127.0.0.1
> doing stuff with 127.0.0.1
> => 3
> 
> But I can't work out how to invoke an initial IRB instance with my own
> 'main' object from the start. I've tried going through the source, but I get
> lost in Contexts and Workspaces well before I get to subirb.rb :-) I'd also
> prefer to implement it in a way which uses a 'standard' interface to Irb,
> such that it won't break with a future version of Ruby.
> 
> Any clues gratefully received.
> 
> Thanks,
> 
> Brian.

The following drops into (or _back_ into) an irb session. (Customizing 
the prompt is another matter, and I don't remember how to do that, but 
it might be findable on ruby-talk.)

(I use typically this in a long running process. I set my INT handler 
and top-level exception handlers to start_session on some main object. 
So ^C drops into irb, and ^D jumps back out.)


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

     workspace = WorkSpace.new(*args)

     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 x with current binding"
   IRB.start_session(binding, x)
   puts "\nRestarted irb shell for x with current binding"
   $irb.eval_input
   puts "\nExited irb shell"
   p x
end



-- 
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407