From: "Chr. Rippel" <chr_news@...>
Date: 2002-01-09T04:00:18+09:00
Subject: Re: class name reported differently in different contexts

"ts" <decoux@moulon.inra.fr> wrote
....
>  Well, for me this is not a technical problem.
>
>  ::inherited can raise an error and the class will never exist.
>
>  Actually ruby give a classpath to a class when it is sure that the class
>  will exist, before this the class not yet exist and has only a classid
Well,

you could put the call to #inherited in a rescue clause and if necessary
remove the newly created constant and re-raise the offending exception
(see the ruby solution at the end).
I am also not sure if I follow your and Matz logic on this matter
completely. First of all anybody throwing an exception in a call to
#inherited definitely deserves the pain to clean up the mess he/she
probably created. Furthermore the current scheme does not protected
you in a threaded enviroment and exceptions can occur at any time
during class construction (which in Ruby are closer to class
modification) anyway.

---------
begin
  class A
    raise "tuff luck" if (rand(2) == 0)
    def bla; end
  end
rescue RuntimeError => mes
  puts mes
end
---------

That said I am not particularly opinionated  about this matter since I
don't like the reliance on (constant)names as a programming technique
in general.

/Christoph

---------
class Module
  private
  def correct_name (name,up = Object, &body)
    s = self
    begin
      if block_given?
        Class.new up do |k| s.const_set name, k end.class_eval(&body)
      else
        Class.new up do |k| s.const_set name, k end
      end
    rescue Exception => mes
      begin
        s.send :remove_const, name
      rescue NameError
      end
      raise mes
    end
  end
end

def correct_name (name,up = Object, &body)
  begin
    if block_given?
      Class.new up do |k| Object.const_set name, k end.class_eval(&body)
    else
      Class.new up do |k| Object.const_set name, k end
    end
  rescue Exception => mes
    begin
      Object.send :remove_const, name
    rescue NameError
    end
    raise mes
  end
end



# example
class Base
   def Base.inherited(sub)
     puts "In #inherited, subclass name is #{sub}"
     raise "bad" if rand(2)==0
   end
end


begin
  module Mod
  correct_name :Sub, Base do
    def bla; end
    puts "In class definition, subclass name is #{self}"
  end
  end
rescue Exception => mes
  puts mes
end


begin
correct_name :T, Base
rescue Exception => mes
  puts mes
end