Patch to IRB to allow a custom context.

core_ext-irb.rb

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
     end

     workspace = WorkSpace.new(*args)

     if @CONF[:SCRIPT]
       $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
   end
end

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

usage.rb

# Instance context
class Foo
  def do_stuff
    local_var = 'this is local'
    # Run IRB in the context of self.
    IRB.start_session(self)
  end
end


# Binding to an object
foo = 'some fooking string'
# Context will be the string instance in 'foo'
IRB.start_session(foo)