From: James Edward Gray II <james@...>
Date: 2006-10-04T01:28:47+09:00
Subject: Re: Private visibility should be removed from Ruby 2 [was: Caveats with #method_missing]

On Oct 3, 2006, at 11:07 AM, Tomasz Wegrzanowski wrote:

> On 10/3/06, James Edward Gray II <james@grayproductions.net> wrote:
>> 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
>
> Then could you explain, whether:

These are probably questions better asked of irb, but I'll try...

>  a = Name.new('foo', 'bar')
>  a.instance_eval { a.sortable } # correct or not ?

I have no idea what "correct" means here, but I can tell you that  
Ruby allows protected methods to be called function-style for the  
current object and method style for another object of the same class:

 >> a.instance_eval { a.sortable } # correct or not ?
NoMethodError: protected method `sortable' called for #<struct Name  
first="foo", last="bar">
         from (irb):20
         from (irb):20
         from :0
 >> a.instance_eval { sortable }
=> ["bar", "foo"]
 >> a.instance_eval { self.sortable }
NoMethodError: protected method `sortable' called for #<struct Name  
first="foo", last="bar">
         from (irb):23
         from (irb):23
         from :0

You do seem to be able to use either style in method definitions for  
the current object though:

 >> 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)
 >>     self.sortable <=> other.sortable
 >>   end
 >> end
=> nil
 >> Name.new("James", "Gray") <=> Name.new("Dana", "Gray")
=> 1

>  Name.instance_eval { a.sortable } # correct or not ?

Well, it blows up and I consider that "correct", yes.  You are inside  
the Name class here, not an instance of that class.

James Edward Gray II