From: James Edward Gray II <james@...>
Date: 2006-10-03T23:57:57+09:00
Subject: Re: Private visibility should be removed from Ruby 2 [was: Caveats with #method_missing]

On Oct 3, 2006, at 7:20 AM, Tomasz Wegrzanowski wrote:

>> |* remove "protected" visibility completely
>
> Nobody uses "protected" (0 uses in standard library - can anybody  
> find some
> code that actually uses it ?). Nobody understands it.

I understand it just fine and have used it before.  Here's an example  
where it might be needed:

 >> class Name < Struct.new(:first, :last)
 >>   def full
 >>     "#{first} #{last}"
 >>   end
 >>
?>   def last_first
 >>     "#{last}, #{first}"
 >>   end
 >>
?>   def sortable
 >>     [last, first]
 >>   end
 >>   protected :sortable
 >>
?>   def <=>(other)
 >>     sortable <=> other.sortable
 >>   end
 >> end
=> nil
 >> names = [ %w[James Gray],
?>           %w[Dana Gray],
?>           %w[Joe Fair] ].inject(Array.new) { |a, n| a + [Name.new 
(*n)] }
=> [#<struct Name first="James", last="Gray">, #<struct Name  
first="Dana", last="Gray">, #<struct Name first="Joe", last="Fair">]
 >> # OK, because protected allows the call to other.sortable:
?> names.sort.map { |n| n.last_first }
=> ["Fair, Joe", "Gray, Dana", "Gray, James"]
 >> # Not OK, because sortable is for internal use only:
?> names.first.sortable
NoMethodError: protected method `sortable' called for #<struct Name  
first="James", last="Gray">
         from (irb):28
         from :0

James Edward Gray II