From: Robert Klemme <shortcutter@...>
Date: 2007-02-05T07:25:07+09:00
Subject: Re: method visibility VS accessibility

On 04.02.2007 22:49, Thai Le wrote:
> I've done java for a few years and ruby is pretty new to me. In java, a
> method has visibility(private, protected, public) and

Actually there are four of them: you have to add "package" visibility to 
the list. :-)

> accessibility(static, non-static); however, in ruby how can I declare
> the method: "public static method1"? It seem that the default visibility
> of a method is public in ruby, am i correct?

Yes.  Strictly speaking there are no static methods in Ruby.  But it has 
the concept of singleton methods that are defined for a single instance 
only.  And since classes are just ordinary objects you can define 
instance methods of class objects and achieve basically the same as with 
Java's static methods:

class Foo
   def self.a_class_method
     # ...
   end

   def an_instance_method
     self.class.a_class_method
     self.another_class_method
   end
end

def Foo.another_class_method
   # ...
end

> One morething is that java program starts from "public static main()".
> What is the entry point to ruby program?

The situation is a bit different because Ruby is interpreted.  If you 
want, you can view the root script you invoke as the body of main, i.e., 
code is executed top down.  However, part of this execution are class, 
method and constant definitions.  Invocation arguments are accessible 
via ARGV (and also ARGF which is a special shortcut which will read from 
all files in ARGV).  So, strictly speaking there is no equivalent of 
Java's and C's "main" but the functionality is there.

Kind regards

	robert