From: Ed Sinjiashvili <edsin@...>
Date: 2002-04-27T14:34:58+09:00
Subject: Re: appending methods to class inside module

Hello Ian,

IM> The protected method was in class String and the method call was made
IM> from an unrelated class, but it was made from an instance variable
IM> that itself was of type String.

You should judge your right on calling someone's methods depending on
self at the point of *invocation*.

Public methods: can be called no matter who self is
Protected methods: can be called only if self has the same type as
the target object (i.e. self if the object of the same (or descendent)
class as the target)
Private methods: can be called only on self

So, in order to call your protected method of String, you should be
a String or some kind of it. Since your Foo::Bar is obviously not a
String you can't call String's protected methods. But you can become a
kind of String:

whailer% cat test.rb
class String
  def check
    if self.length > 2048
      puts "bad"
    else
      puts "good"
    end
  end

  protected :check
end

module Foo
  class Bar < ::String
    def initialize ; end
    def baz
      "hello".check
    end
  end
end

Foo::Bar.new.baz
"don't do that".check
whailer%

whailer% ruby test.rb
good
test.rb:23: protected method `check' called for "don't do that":String (NameError)
whailer%

-- Ed