From: daz <dooby@...10.karoo.co.uk>
Date: 2004-06-19T17:23:20+09:00
Subject: Re: a newbie question about main, Object...


Kevin Bullock wrote:
>
> This thread brought up an interesting idea in my mind. If one truly
> wants to define a top-level method, perhaps you could do this:
>
> irb(main):001:0> class << self
> irb(main):002:1>   def foo; puts "singleton method of top-level Object
> instance"; end
> irb(main):003:1> end
> => nil
> irb(main):004:0> foo
> singleton method of top-level Object instance
> => nil
> irb(main):005:0> Object.new.foo
> NoMethodError: undefined method `foo' for #<Object:0x4c6dc>
>          from (irb):5
>
> The usefulness of this depends on what you want a top-level method for.
> If you want a globally accessible method, the foregoing approach
> doesn't work:
>
> irb(main):006:0> class Demo
> irb(main):007:1>   def bar; foo; end
> irb(main):008:1> end
> => nil
> irb(main):009:0> Demo.new.bar
> NameError: undefined local variable or method `foo' for #<Demo:0x216e0>
>          from (irb):7:in `bar'
>          from (irb):9
>
> But then, globally accessible methods are generally frowned upon in
> pure OO design. If, on the other hand, you're hacking out a quick
> script to do something useful, and you want a top-level method that
> only needs to be accessed at top-level, this works quite well *and*
> maintains good information hiding practice.
>
> [...] is this an established idiom?
>

Not one that I've seen a lot of.

This script could be useful for self-hypnosis :)

def self.roo
  puts "*** (singleton roo) [#{self}] (#{self.class} instance) ***"
  super
end

class Object
  def roo
    puts "*** (   object roo) [#{self}] (#{self.class} instance) ***"
    super
  end
end

module Kernel
  def roo
    puts "*** (   kernel roo) [#{self}] (#{self.class} instance) ***"
  end
end

roo

#=> *** (singleton roo) [main] (Object instance) ***
#=> *** (   object roo) [main] (Object instance) ***
#=> *** (   kernel roo) [main] (Object instance) ***


daz