# IRB as test interface to existing object **URL:** \ **Category:** ruby-talk\ **Created:** [17 March 2007 13:54 UTC](https://rubytalk.org/t/irb-as-test-interface-to-existing-object/36225 "2007-03-17T13:54:34Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![Brian\_Candler](https://avatars.discourse-cdn.com/v4/letter/b/5f9b8f/32.png) [@Brian\_Candler](https://rubytalk.org/u/Brian_Candler)\ **Post date:** [17 March 2007 13:54 UTC](https://rubytalk.org/t/irb-as-test-interface-to-existing-object/36225/1 "2007-03-17T13:54:34Z")
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") =\> #\ irb(main):013:0\> irb obj irb#1(#\):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 馃檪 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. ---
**Author:** ![Joel\_VanderWerf1](https://avatars.discourse-cdn.com/v4/letter/j/94ad74/32.png) [@Joel\_VanderWerf1](https://rubytalk.org/u/Joel_VanderWerf1)\ **Post date:** [17 March 2007 16:42 UTC](https://rubytalk.org/t/irb-as-test-interface-to-existing-object/36225/2 "2007-03-17T16:42:42Z")
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 > 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") > =\> #\ > irb(main):013:0\> irb obj > irb#1(#\):001:0\> do\_stuff 3 > 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 馃檪 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 > **路路路** > > -- >        vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407 ---
**Author:** ![Brian\_Candler](https://avatars.discourse-cdn.com/v4/letter/b/5f9b8f/32.png) [@Brian\_Candler](https://rubytalk.org/u/Brian_Candler)\ **Post date:** [17 March 2007 17:40 UTC](https://rubytalk.org/t/irb-as-test-interface-to-existing-object/36225/3 "2007-03-17T17:40:37Z")
> The following drops into (or \_back\_ into) an irb session. This works perfectly, thank you (great to get command history!) It also looks suspiciously like IRB.start in /usr/lib/ruby/1.8/irb.rb - shame that doesn't take a second optional parameter for the workspace. > (Customizing > the prompt is another matter, and I don't remember how to do that, but > it might be findable on ruby-talk.) Just defining a to\_s method on the object works well enough for me. I have also found more details about IRB.conf in "man irb" (actually "man irb1.8" on this Ubuntu box) Thanks again, Brian. > **路路路** > > On Sun, Mar 18, 2007 at 01:42:42AM +0900, Joel VanderWerf wrote: