From: "John N. Alegre" <info@...>
Date: 2006-02-28T04:58:36+09:00
Subject: Confused about "private"??


I have a confusion in Ruby's way of dealing with "private" instance methods.

"Private" means that the method is accessible only within the class, and it
is callable only in "function form," with self (implicit or explicit) as a
receiver." "Protected" gives access to the method in subclasses.

as is the case in Java or Obj C

However ... here is some very simple code that is not doing what I
expect ...

####################################################
# Example One
# Works as expected
####################################################
/usr/bin/ruby -w

class MyClass
protected
 def say
        puts "Hello"
 end
public
        def sayit
                self.say
        end
end

class AClass < MyClass
end

puts "Start"
r = MyClass.new
r.sayit
t = AClass.new
t.sayit
#########################################
salamanca:~/Hack/Hack04/Ruby1 jna$ ./int.rb 
Start
Hello
Hello

That is exactly as I expected with the subclass having access to a super
"protected" method.

####################################################
# Example Two
# Not as expected
####################################################
/usr/bin/ruby -w

class MyClass
private
 def say
        puts "Hello"
 end
public
        def sayit
                self.say
        end
end

class AClass < MyClass
end

puts "Start"
r = MyClass.new
r.sayit
t = AClass.new
t.sayit

#########################################
salamanca:~/Hack/Hack04/Ruby1 jna$ ./int.rb 
Start
../int.rb:10:in `sayit': private method `say' called for #<MyClass:0x26148>
(NoMethodError)
        from ./int.rb:19

What I expected to see here is the first call to r.sayit retruning "Hello"
as it is calling it's own "private" method.  I expected to see the error on
the second call ot t.sayit.

What am I missing?  This is not to the best of my knowledge the way things
are in Java.

Thanks
john